K2PDFOPT重排PDF，设置对比度，优化排版

早期在读研的时候，就在找把PDF扫描文件清晰化，有些扫描书籍出来的PDF，又是歪的，又是糊的，看起来非常费劲，网上搜索 PDF 对比度 PDF 清晰化，一般的方案就是下载adobe acrobat，然后到处图片，放入PS处理，这个方案还是洗洗睡吧，几百个PDF，你让我这样搞？

近段时间，突然在思考，既然国内电子书看PDF可以对PDF进行重新排版，进行字体大小设置、对比度设置等，说明这个肯定是有办法的。后来把kindle也拿出来看了下，试了下越狱+KOReader方案，也是可以重排PDF的，而且效果真的非常不错。

最终，找到了K2PDFOPT，这个是国外的一个非常成熟的PDF优化工具，硬核老外写的，但都是一堆英文资料，特别是一大堆的参数设置，绝对吓跑所有人，但经过我2-3天的调试，得出结论，这个玩意儿绝对好，肯定能解决我的问题。

K2PDFOPT可以用在2个地方，一个是电子书上，一个是电脑上优化PDF看起来舒服些

电子书这个没啥好说的，国内的电子书基本都有这个功能，kindle的KOReader内核就是用K2PDFOPT的。

这篇文章，我专门分享如何在电脑上优化优化PDF看起来舒服些，先看下结果吧。

这个是歪的原始稿件

这个是优化后的结果

对于字体模模糊糊的处理对比

感觉如何？是不是赞爆了

完整参数如下：
-as -n- -wrap- -col 1 -vb -2 -w 1s -h 1s -c -t- -f2p -2 -m 0 -om 0 -pl 0 -pr 0 -pt 0 -pb 0
上面参数目的：

1. 把歪的拉正
2. 把字体清晰化、纸质化、拉高对比度
3. 完全符合原有PDF的排版

下面是我的调试过程，可供参考

1. -n -wrap- -col 1 -vb -2 -t -p 41,42
2. -n -wrap- -col 1 -vb -2 -t -er 1 -p 41,42 //针对1，在有-n情况下，-er无效
3. -wrap- -col 1 -vb -2 -t -p 41,42 //针对1，拿掉-n，整体已经开始优化了
4. -n -col 1 -vb -2 -t -p 41,42 // 针对1，拿掉 -wrap- ，也没有关系，因为有-n
5. -col 1 -vb -2 -t -p 41,42 针对4，但如果-n也拿掉，就开始换行了，排版一下子都乱了
6. -wrap- -vb -2 -t -p 41,42 如果拿掉-n 并且强制不换行-wrap-，但这时拿走了-col 1 排版也会乱，因为会预测一些2栏排版，对于电脑上看电子书，咩有必要
7. -wrap- -col 1 -t -p 41,42 针对3，拿走了-vb -2，相当于默认-vb 1.75有些标题开始变的很大
8. -vb -1 -wrap- -col 1 -t -p 41,42 针对3，把-vb设置成-1，所有的行间距都变的很小
9. -vb 3 -wrap- -col 1 -t -p 41,42 针对3，把-vb设置成3，仍旧标题开始变的很大
10. -wrap- -col 1 -vb -2 -t- -p 41,42 针对3，设置-t-，使得-t无效，但好像不明显
11. -as -wrap- -col 1 -vb -2 -t- -p 41,42 针对10，发现-t-不是无效，而是页面是歪的，所有没有trim边上空白成功而已
12. -as -wrap- -col 1 -vb -2 -t -p 41,42 针对11，-t有效果了，边上被割了，设置成-t-就会留白
13. -bp-- -as -wrap- -col 1 -vb -2 -t- -p 41,42 把bp关掉，不然会分页产生大量空白
14. -bp-- -as -wrap- -col 1 -vb -2 -t- -p 19 -w 900 -h 1350 这个宽和高其实就是设置一个比例关系

这个是macos的运行界面：

当然还有windows的图形界面版本，但也没啥差别，那个图形化的界面，我也就呵呵了

下面是完整的参数说明，仅供无法上国外网站的朋友备用参考：（原始地址：https://www.willus.com/k2pdfopt/help/options.shtml）

LIST OF K2PDFOPT COMMAND-LINE OPTIONS
This is the entire list of k2pdfopt command-line options that come directly from the "usage" output of k2pdfopt. You can get this list by typing ? at the interactive menu or with the command-line option -?.

To see how to use these options with k2pdfopt, see the "Customizing K2pdfopt" menu at the left, e.g. using a shortcut or using an environment variable. Many of these options have equivalents in the interactive menu. You can also type any of these options into the "Additional Options" text field in the MS Windows GUI to enable options that are otherwise not accessible from the GUI.

k2pdfopt v2.53 (w/MuPDF,DjVuLibre,OCR) (c) 2020, GPLv3, http://willus.com
 Compiled Jul 18 2020 with Gnu C (Mingw64) v9.3.1 for Win64 on x64.
 
 
usage: k2pdfopt [opts] 
 
 
(Or just drag a PDF or DJVU (.djvu) file to this icon.)
 
 
Attempts to optimize PDF (or DJVU) files (especially two-column ones) for
 display on the Kindle (or other mobile readers/smartphones) by looking for
 rectangular regions in the file and re-paginating them without margins and
 excess white space. Works on any PDF or DJVU (.djvu) file, but assumes it
 has a mostly-white background. Native PDF files (not scanned) work best.
 
 
If given a folder, k2pdfopt first looks for bitmaps in the folder and if
 any are found, converts those bitmaps to a PDF as if they were pages of a
 PDF file. If there are no bitmaps in the folder and if PDF files are in
 the folder, then each PDF file will be converted in sequence.
 
 
Output files are always .pdf and have _k2opt added to the source name by
 default (see -o option to specify alternate output name.)
 
 
K2PDFOPT environment variable
 
 
You can supply command-line options via the environment variable K2PDFOPT,
 for example,
 
 
 set K2PDFOPT=-ui- -x -j 0 -m 0.25
 
 
Command line options from the command line take precedence over the ones in
 the environment variable K2PDFOPT.
 
 
Command Line Options
 
 
-?[-] [pattern] Show [don't show] usage only (no file processing).
 If pattern is specified, only options with text matching
 the pattern are shown. The pattern can use * as a wild
 card, e.g. -? -col. Use -?- to turn off usage.
 Combine with -ui- to get something you can redirect
 to a file.
 -a[-] Turn on [off] text coloring (use of ANSI color codes) on
 the screen output. Default is on.
 -ac[-] [] Auto crop. For books or papers that have dark edges
 due to copying artifacts, this option will attempt to
 automatically crop out those dark regions so that k2pdfopt
 can correctly process the source file. The 
 factor is from 0 to 1. Higher is more aggressive cropping.
 Default if not specified is 0.1. See also -m.
 Default value is off (-ac-).
 Note that autocropping does not work on cropped regions
 created with -cbox. See -dw for a discussion about this.
 -as[-] [] Attempt to automatically straighten tilted source pages.
 Will rotate up to +/- degrees if a value is
 specified, otherwise defaults to 4 degrees max. Use -1 to
 turn off. Default is off (-as -1 or -as-).
 Note that autostraighten does not work on cropped regions.
 See -dw for a discussion about this.
 -author  Set the author metadata / property of the PDF output
 file(s). Default is to use the author of the source document
 (-author "").
 -bmp[-]  Generate [do not generate] a bitmap rendering of converted
 page number  and write it to file k2pdfopt_out.png.
 If this option is used, no other files are written, i.e. the
 complete conversion is NOT done--ONLY the bitmap file is
 written. If -sm is also specified, then the bitmap is of
 marked source page . If -bmp-, then  is not
 necessary. Default is -bmp-.
 -bp[+|-|--] [m|] Break [do not break] output pages at end of each input
 page. Default is -bp-. If a numeric value is put after -bp,
 then rather than breaking the output page at the end of each
 input page, a gap is inserted of that many inches, e.g.
 -bp 1 will insert a 1-inch gap between contents of each
 input page. Special option -bp+ will break the pages at
 the green boundaries between region as marked by the -sm
 option (see -sm). If bookmark information is available
 and -toc is specified (on by default) page breaks will be
 inserted in the converted file at each bookmark unless -bp--
 is specified. If "-bp m" is specified, then a page break
 is inserted after each major (red-box) section. This can
 help prevent text selection overlap problems in native output
 mode. See also -toc, -bpl.
 -bpc  Set the bits per color plane on the output device to .
 The value of  can be 1, 2, 4, or 8. The default is 4
 to match the kindle's display capability. This is ignored
 if the -jpg option is specified.
 -bpl  Insert page break in destination file before each source
 file page listed in . This has the same format
 as the -p option. See also -p, -bp, -toc, -toclist. Default
 is no page list. Example: -bpl 10,25,50,70,93,117,143.
 This automatically sets -bp to it's default value (-bp-).
 -bpm[]  Set a page break mark type and color. This option allows
 you to put colored marks in the PDF file to specify where to
 break pages or where to avoid page breaks.  is either
 1 to force a page break or 2 to prevent a page break until
 next mark.  is an R,G,B triplet, 0-1 for each color
 component, no spaces. For example, to break the page
 wherever the source file has a green dot or short green
 horizontal line: -bpm1 0,1,0. Use  = -1 to clear.
 If you omit the , 1 is assumed.
 -c[-] Output in color [grayscale]. Default is grayscale.
 -cbox[|u|-]  Similar to the -grid option, but allows you to
 specify exact crop boxes from the source page which will
 then be processed as major (red-box) regions. These regions
 can then become individual output pages or can be processed
 further (searched for columns, re-flowed, etc.) depending on
 what other options are selected. By default, they are
 processed further, like every other major region.
 You may specify the -cbox option multiple times to crop out
 different parts of each source page, each crop being treated
 as a major region. See the -mode command. To have each
 crop box become a new page in the output file, for example,
 use -mode crop, e.g.
 k2pdfopt myfile.pdf -mode crop -cbox 2in,3in
  has the format ,,,
 where all values are specified from the upper-left corner of
 the source page, with units, like the -w and -h options,
 except that the default units for -cbox are inches. If only
  and  are specified, then  and 
 extend to the edge of the page.
 Example: -cbox 1in,1in,6in,9in (same as -cbox 1,1,6,9).
 This specifies a crop box that is 6 x 9 inches and which
 has an upper left corner which is 1 inch from the left
 and top of the source page.
 Use -cbox- to clear all cropboxes, which defaults back to
 processing every page without any crop boxes.
 You can use a page list, , to specify on which
 pages to apply the cropboxes.
 Examples:
 -cbox5-51o ... applies the cropbox on pages 5,7,9,...,51.
 ('o' = odd. Use 'e' for even.)
 -cbox1,2-5,13,15 ... applies the cropbox on pages 1,2,3,
 4,5,13, and 15.
 -cboxc  ... applies  to the cover image.
 (see -ci option.)
 Be sure not to put a space between -cbox and the page list.
 Use -cboxu to set a crop box for all unspecified pages.
 E.g. -cbox1-10  -cboxu  will apply  to
 all pages 1 to 10 and  to all other pages.
 The default is no crop boxes (-cbox-). See also -m, -ac.
 USAGE NOTE: Once you specify -cbox at least one time, only
 the crop boxes you specify (and any associated page ranges)
 are processed/converted by k2pdfopt. No other pages or
 regions are processed. So if you want to specify a special
 cropbox for the first page, for example, but then have all
 remaining pages treated entirely, you must specify this:
 -cbox1 ... -cboxu 0,0
 (-cboxu 0,0 applies a full-page cropbox to all other
 pages. u = unspecified.)
 The -cbox2- 0,0 will set the cropbox for pages 2 and beyond
 to the full page size.
 See also: -ibox.
 -cg  Minimum column gap width in inches for detecting multiple
 columns. Default = 0.1 inches. Setting this too large
 will give very poor results for multicolumn files. See also
 -cgmax.
 -cgmax  Max allowed gap between columns in inches. If the gap
 between two regions exceeds this value, they will not be
 considered as separate columns. Default = 1.5. Use -1 for
 no limit (disable). See also -cg.
 -cgr  Set column-gap range, 0 - 1. This is the horizontal range
 over which k2pdfopt will search for a column gap, as a
 fraction of the page width. E.g. -cgr 0.5 will search
 from 0.25 to 0.75 of the page width for a column gap.
 Set this to a small value, e.g. 0.05, to only search for
 column breaks in the middle of the page. Default = 0.33.
 -ch  Minimum column height in inches for detecting multiple
 columns. Default = 1.5 inches.
 -ci[-]  Specify a cover image for the first page of the converted
 PDF.  can be a bitmap file (png or jpg) or can be
 a page from a PDF file, e.g. myfile.pdf[34] would use page 34
 of myfile.pdf. You can just specify an integer, e.g. -ci 50
 to use page 50 of the source file being converted as the
 cover page. Default is -ci-, which is no cover image.
 NOTE: -ci only works with bitmapped output--it does not
 (yet) work with native PDF output.
 -cmax  Set max contrast increase on source pages. 1.0 keeps
 contrast from being adjusted. Use a negative value to
 specify a fixed contrast adjustment. Def = 2.0.
 See also -er.
 -col  Set max number of columns.  can be 1, 2, or 4.
 Default is -col 2. -col 1 disables column searching.
 Columns will be displayed left to right unless -r is
 specified, in which case they will be displayed right
 to left. You can use the -go option to override this.
 -colorbg (or -colorfg) |[,|[,...]]
 Map the color white (background color, for -colorbg) or the
 color black (text color, for -colorfg) to ,
 where  is a 6-digit hex RRGGBB representation of a
 color, e.g. ffffff for all white, 000000 for all black,
 ff0000 for bright red, etc. If  is not a grayscale
 color, the -c (color output) option will be turned on
 automatically. This option only works with bitmapped output
 (not native--see -n). Grayscale colors between black and
 white will be linearly interpolated between the specified
 -colorbg and -colorfg colors. If the source document has
 colors, only (mostly) grayscale pixels are affected if ! is
 put before the color, e.g. -colorbg !ffffd0
 A bitmap can also be specified, e.g. -colorbg myfile.jpg.
 In this case, the bitmap gets tiled in as the background.
 If you specify a comma delimited list of colors (or bitmaps),
 then consecutive rows of text are colored with the
 consecutive colors. This is a possible way to make the
 rows of text easier to follow, e.g. -colorfg ff0000,00 will
 color alternate rows of text red and black.
 Default is -colorbg "" and -colorfg "" (no mappings).
 -comax  Stands for Column Offset Maximum. The  given is as a
 fraction of the width of a single column, and it specifies
 how much the column divider can move around and still have
 the columns considered contiguous. Set to -1 to revert back
 to how columns were treated in k2pdfopt v1.34 and before.
 Default = 0.3.
 -crgh  Set the min height of the blank area that separates regions
 with different numbers of columns. Default = 1/72 inch.
 -d[-] Turn on [off] dithering for bpc values < 8. See -bpc.
 Default is on.
 -ddr[-] Detect Double Rows. [Expert mode.] By default this is on.
 Use -ddr- to turn off. This option does extra analysis to
 try and separate text rows by looking for double and triple
 rows that may have been missed on the first pass. This can
 have the unintended consequence of breaking up figures
 across pages.
 -de  Defect size in points. For scanned documents, marks
 or defects smaller than this size are ignored when bounding
 rectangular regions. The period at the end of a sentence is
 typically over 1 point in size. The default is 1.0.
 -dev  Select device profile (sets width, height, dpi, and corner
 marking for selected devices). Currently the selection is
 limited.  just has to have enough characters to
 uniquely pick the device. Use -dev ? to list the devices.
 Default is -dev kindle2.
 -dpi  Same as -odpi.
 -dr  Display resolution multiplier. Default = 1.0. Using a
 value greater than 1 should improve the resolution of the
 output file (but will make it larger in file size).
 E.g. -dr 2 will double the output DPI, the device width
 (in pixels), and the device height (in pixels).
 -ds  Override the document size with a scale factor. E.g. if
 your PDF reader says the PDF file is 17 x 22 inches and
 it should actually be 8.5 x 11 inches, use -ds 0.5. Default
 is 1.0.
 -dw[-] [] De-warp [do not de-warp] pages (uses Leptonica de-warp
 algorithms). Default is not to de-warp. Does not work
 for native mode output. Optional  specifies the
 fit order for the dewarping curves. Can be 2, 3, or 4.
 Default is 4.
 [Advanced: You can actually make the fit order a two-digit
 code. E.g. -dw 24 will use 4th-order on each row of text
 but only 2nd-order for columns of displacement (see
 leptonica dewarpFindVertDisparity() in dewarp2.c)]
 Note: de-warping, like auto-straighten and auto-crop, is
 intended for entire pages. It does not work on cropped areas.
 If you want it to work on cropped areas, you should run
 k2pdfopt in two passes--first to create selected crop
 areas (e.g. -mode crop), then to apply dewarping.
 -ehl  Same as -evl, except erases horizontal lines instead of
 vertical lines. See -evl. Default is -ehl 0.
 -er  Use erosion filter on source bitmaps. Makes the text look
 darker. A larger value of  makes the text thicker/darker.
 Try -er 1 or -er 2. Default is 0 (no erosion filtering).
 Use a negative value for  to do the erosion before the
 constrast adjustment is applied. Use a positive value to
 to the erosion after the constrast adjustment is applied.
 This option may magnify scanning defects, so you might want
 to combine with the -de (defect removal) option.
 Has no effect in native mode output. See also -de, -g, -cmax.
 -evl  Detects and erases vertical lines in the source document
 which may be keeping k2pdfopt from correctly separating
 columns or wrapping text, e.g. column dividers. If  is
 zero, this is turned off (the default). If  is 1, only
 free-standing vertical lines are removed. If  is 2,
 vertical lines are erased even if they are the sides of
 an enclosed rectangle or figure, for example.
 -f2p  Fit-to-page option. The quantity  controls fitting
 tall or small contiguous objects (like figures or
 photographs) to the device screen. Normally these are fit
 to the width of the device, but if they are too small or
 too tall, then if =10, for example, they are allowed
 to be 10%% wider (if too small) or narrower (if too tall)
 than the screen in order to fit better. Use -1 to fit
 a tall object entirely within the device screen no matter
 what. Use -2 as a special case--all "red-boxed" regions
 (see -sm option) are placed one per page.
 Use -f2p -3 to fit as many "red-boxed" regions as
 possible on each page without breaking them across pages.
 (see -mode concat).
 Default is -f2p 0. See also -jf, -fr.
 Note: -f2p -2 will automatically also set -vb -2 to
 exactly preserve the spacing in the red-boxed region. If
 you want to compress the vertical spacing in the red-boxed
 region, use -f2p -2 -vb -1.
 -fc[-] For multiple column documents, fit [don't fit] columns to
 the width of the reader screen regardless of -odpi.
 Default is to fit the columns to the reader.
 -fr[-] Figure rotate--rotates wide-aspect-ratio figures to landscape
 so that they best fit on the reader page. Default is not
 to rotate. See also -f2p.
 -fs [+] The output document is scaled so that the median font size in
 the converted file is  points. If the  value
 is followed by a '+', the scaling is adjusted for every
 source page, otherwise the font size is only adjusted once,
 based on the median font size for the entire source document.
 The default is -fs 0, which turns off scaling based on font
 size. The use of -fs overrides the -mag setting.
 -g  Set gamma value of output bitmaps. A value less than 1.0
 makes the page darker and may make the font more readable.
 Default is 0.5. Has no effect with native-mode output.
 See also -er, -cmax.
 -go  Grid order. Override order of processing for a gridded page
 (see -grid) or for multiple columns. The following integer
 codes are used: 1=left-to-right, 2=right-to-left,
 3=top-to-bottom, 4=bottom-to-top. So -go 13 will first go
 left to right, starting at the top row and then working
 towards the bottom row, row by row. -go 31 will go top to
 bottom starting with the left column and then working to the
 right, column by column. The default is 31 unless -r is
 specified, in which case it is 32. For multiple columns,
 only 1 or 2 need be specified.
 -grid x[x][+] Grid the source page into  columns by  rows with
 with  percent overlap. No regard will be made for trying
 to break the page between columns or rows of text. If a +
 is specified, the destination page order will go across and
 then down, otherwise it will go down and then across. To
 turn off gridding, specify a zero value for the columns or
 for the rows. Default is no gridding. The default overlap
 is 2%%. Example: -grid 2x2x5. By default, gridding also
 sets the following options, which can be overridden by
 following the grid option with other command options:
 -n -wrap- -f2p -2 -vb -2 -col 1. For example, if you want
 a column search done on each grid piece, you can put this:
 -grid 2x2 -col 2. See also -go, -cbox.
 -gs[-][-] Force use of Ghostscript instead of MuPDF to read PDFs.
 K2pdfopt has built-in PDF translation (via the MuPDF
 library) but will try to use Ghostscript if Ghostscript
 is available and the internal (MuPDF) translation fails
 (virtually never happens). You can force Ghostscript to
 be used with this -gs option. Use -gs- to use Ghostscript
 only if MuPDF fails. Use -gs-- to never use Ghostscript.
 Download ghostscript at http://www.ghostscript.com.
 -gtc  Threshold value for detecting column gaps (expert mode).
 Sets how many of the pixels in the column shaft can be
 non-white (total height of a line crossing the shaft in
 inches). See also -gtr. Default = .005.
 -gtr  Threshold for detecting gaps between rows (expert mode).
 This option is commonly adjusted when lines of text in the
 source file are too close together or slightly overlap and
 don't have a clean gap between them. It effectively sets
 how clean that gap has to be in order for k2pdfopt to
 consider that there are separate rows of text. It does
 this by setting the maximum total black pixels, in inches,
 on average, that can be in each row of pixels before the gap
 is no longer considered a gap. A higher value makes it
 easier to detect gaps between rows of text. Too high of a
 value may inadvertently split figures and other graphics.
 For documents with nice clean spaces between each row of
 text, this setting should not need to be adjusted.
 Default = 0.006. See also -rsf.
 -gtw  Threshold for detecting word gaps (expert mode).
 See -gtr. Default = .0015.
 -gui[-] Use [don't use] graphical user interface (MS Windows only).
 If k2pdfopt is started from a console (command-line), the
 default is not to launch the gui unless there are no command-
 line options given. If k2pdfopt is launched via its icon,
 then the default is to launch the GUI.
 -guimin[-] Start the k2pdfopt GUI minimized. Def = not minimized.
 -h [in|cm|s|t|p|x] Set height of output device in pixels, inches, cm,
 source page size (s), trimmed source region size (t),
 pixels (p), or relative to the OCR text layer (x).
 The default units are pixels (p), and the default value
 is 735 (the height of the Kindle 2 screen in pixels).
 Examples:
 -h 6.5in Sets the device height to 6.5 in
 (using the output dpi to convert to
 pixels--see -dpi).
 -h 1.5s Sets the device height to 1.5 times the
 source page height (same as -h -1.5).
 -h 1t Sets the device height to whatever the
 trimmed page height is (you can follow
 -mode copy with -h 1t to make the output
 page height equal to the crop box height.
 -h 0.5x Sets the device height to half of the
 height of the box exactly surrounding
 the OCR text layer on the source page.
 See also -w, -dpi, -dr.
 -hy[-] Turn on [off] hyphen detection/elimination when wrapping
 text. Default is on.
 -i Echo information about the source file (PDF only).
 Disables all other processing.
 -ibox[|-|u]  Same as -cbox (see -cbox), except that these
 boxes are ignored by k2pdfopt. This is done by whiting out
 the boxes in the source bitmap. For native output, the
 area in the -ibox will not affect the parsing of the source
 file, but it may still be visible in the output file.
 Default is no iboxes (-ibox-). See also -cbox.
 -idpi  Set pixels per inch for input file. Use a negative value
 as a multiplier on the output dpi (e.g. -2 will set the
 input file dpi to twice the output file dpi (see -odpi).
 Default is -2.0.
 -j -1|0|1|2[+/-] Set output text justification. 0 = left, 1 = center,
 2 = right. Add a + to attempt full justification or a -
 to explicitly turn it off. The default is -1, which tells
 k2pdfopt to try and maintain the justification of the
 document as it is. See also -wrap.
 -jf 0|1|2 [] Set figure (tall region) justification. If a figure
 has left or right margins available, this option allows
 you to set the justification differently than the text.
 E.g. you can center figures with -jf 1. If you want to
 specify a minimum height for figures (e.g. minimum region
 height where this justification applies), you can tack it
 on at the end, e.g. -jf 1 1.5 to center any region taller
 than 1.5 inches. Default is 0.75 inches for the minimum
 height and to use the same justification on figures as
 the rest of the document (-jf -1). See also -f2p to fit
 small or tall figures to the page.
 -jfc[-|+] Attempt [do not attempt] to keep figure captions joined
 with their figures. If you specify -jfc+, k2pdfopt will
 also try to detect figure captions in multi-column documents.
 This is not done by default because k2pdfopt will sometimes
 (more often than not, in my experience) incorrectly choose
 the multi-column layout if it is also trying to detect what
 is a figure caption. See also -cg, -cgmax, -cgr, -crgh.
 Default = -jfc.
 -jpg [] Use JPEG compression in PDF file with quality level
  (def=90). A lower quality value will make your
 file smaller. See also -png. Use of -jpg is incompatible
 with the -bpc option.
 -l  See -ocrlang.
 -lang  See -ocrlang.
 -ls[-][pagelist] Set output to be in landscape [portrait] mode. The default
 is -ls- (portrait). If an optional pagelist is specified,
 only those pages are affected--any other pages are done
 oppositely. E.g. -ls1,3,5-10 would make source pages 1, 3
 and 5 through 10 landscape.
 -m[l|t|r|b] [][,[units][,...]] Set global crop margins for
 every page. If more than one value is given (comma-delimited
 with no spaces in between), the order is left, top, right,
 bottom, e.g. -m ,,,. You can also
 use the more powerful -cbox option to do this same thing.
 The default units are inches. For available units and their
 descriptions, see -h.
 Examples:
 -m 0.5cm
 Sets all margins to 0.5 cm.
 -m 0.5cm,1.0cm
 Sets the left margin to 0.5 cm and all the other
 margins to 1.0 cm.
 -m 0.2in,0.5in,0.2in,0.5in
 Sets the left and right crop margins to
 0.2 inches and the top and bottom to 0.5 inches.
 -mt 1cm
 Sets the top margin to 0.5 cm.
 -m -0.1x,-0.1x,1.1x,1.1x
 With the 'x' unit, the behavior is a little
 different. Rather than specifying the widths
 of each margin, you specify the position of
 the crop box relative to the OCR text layer
 in the source file, where 0x,0x,1x,1x would
 exactly bound the OCR text layer.
 The default crop margins are 0 inches.
 [NOTE: The default was 0.25 inches for all margins before
 v1.65.]
 See also -cbox and -ac to autocrop scanning artifacts.
 -mag  Magnify the converted document (text) size by .
 Default is -mag 1 (no magnification). See also -fs.
 -mc[-] Mark [don't mark] corners of the output bitmaps with a
 small dot to prevent the reading device from re-scaling.
 Default = mark.
 -mode  Shortcut for setting multiple options at once which
 determine the basic way in which k2pdfopt will behave.
 Available modes are:
 copy "Copy" mode. This isn't really intended for
 use with an e-reader. It just creates a
 bitmapped copy of your source document at the
 exact same dimensions. This can be useful in
 order to eliminate any font compatibility
 issues or if you want to eliminate selectable
 text (follow with -mode copy with -ocr-).
 The equivalent settings are -n- -wrap- -col 1
 -vb -2 -w 1s -h 1s -dpi 150 -rt 0 -c -t- -f2p
 -2 -m 0 -om 0 -pl 0 -pr 0 -pt 0 -pb 0 -mc-.
 Use -odpi to select the bitmap resolution.
 Note 1: Use -mode copy -n if you want an exact
 copy (output in native mode).
 Note 2: The default gamma and contrast settings
 are not reset by -mode copy. If you
 want a perfect copy, do this:
 -mode copy -gamma 1 -s- -cmax 1
 fp "Fit Page" mode. Also can use -mode fitpage.
 Fits the entire contents of each source page
 onto the reader display. Same as -n -wrap- -col 1
 -vb -2 -f2p -2 -t.
 fw "Fit Width" mode. Fits the text to the width
 of the reader in landscape mode without doing any
 text re-flow. This is the best way to preserve
 the original layout of the source document.
 To fit to the reader width in portrait mode, add
 -ls- after -mode fw to turn off landscape.
 The -mode fw option is equivalent to -n -wrap-
 -col 1 -vb -2 -t -ls. It was inspired by SoPDF's
 "fit width" option. Can also use -mode sopdf
 or -mode fitwidth
 2col "Two-column" mode. Same as -n -wrap- -col 2
 -vb -2 -t. Optimizes for a 2-column scientific
 article with native PDF output.
 tm "Trim margins" mode. Same as -mode copy, but
 sets the output to be trimmed to the margins and
 the width and height of the output to match the
 trimmed source pages. Also uses native mode.
 Equivalent to -n -wrap- -col 1 -vb -2 -f2p -2 -t
 -w 1t -h 1t -rt 0 -c -m 0 -om 0 -pl 0 -pr 0 -pt 0
 -pb 0 -mc-. Can also use -mode trim.
 crop "Crop" mode. Used with the -cbox option, this
 puts each cropped area on a separate page,
 untrimmed, and sizes the page to the cropped
 region. Same as -wrap- -col 1 -vb -2 -w 1t -h 1t
 -t- -rt 0 -c -f2p -2 -m 0 -om 0 -pad 0 -mc- -n
 concat "Concatenation" mode. Similar to -mode crop,
 but keeps the output pages the same size as the
 source pages and fits as many crop-boxed regions
 onto each new output page as possible without
 breaking them across pages. Equivalent to: -n
 -wrap- -col 1 -vb -2 -t- -f2p -3 -fc- -w 1s -h 1s
 -ocr-
 def "Default" mode. This is the mode you get if you
 run k2pdfopt with no customized options. It is
 equivalent to -wrap -n- -col 2 -ocr m -vb 1.75
 -dev k2 -rt auto -c- -t -f2p 0 -m 0 -om 0.02 -ls-
 You can modify modes by overriding their options after
 specifying the mode, e.g. -mode fw -vb -1.
 -n[-] Use "native" PDF output format. NOTE: if you want native
 PDF output, it's probably best to use a -mode option like
 -mode fitwidth or -mode 2col, both of which automatically
 turn on native PDF output and optimize other settings for it.
 Native PDF output preserves the native source PDF contents,
 i.e. the output PDF file is not rendered as a sequence of
 bitmapped pages like in the default k2pdfopt output mode.
 Instead, the source PDF's native content is used along with
 additional PDF instructions to translate, scale, and crop
 the source content. With native PDF output, if the source
 file has selectable text, the text remains selectable in
 the output file. The output file can also be zoomed
 without loss of fidelity. This may also result in a
 smaller output file (but not always). By default, native
 PDF output format is turned off. See also -mode.
 NOTES:
 1. Native PDF output cannot be used with text wrapping
 on (see -wrap option). Turning it on will disable
 text wrapping.
 2. Native PDF output is not recommended for source
 files which are scanned (there is no benefit unless
 the scanned document includes a layer of OCR text).
 3. Native PDF output is incompatible with OCR (see -ocr),
 though OCR is typically not necessary if the native PDF
 contents are kept. Turning on native PDF output will
 disable OCR.
 4. Native PDF output can only be used with PDF source
 files (it does not work with DJVU source files).
 5. Contrast adjust, gamma correction, and sharpening
 are disabled with native PDF output.
 6. It is recommended that you use -vb -2 with native PDF
 output, particularly if you are having difficulty
 selecting/searching text in the output PDF file.
 7. This option works well with -mode fw, -mode 2col, or
 with the -grid option. It is used by default in those
 cases.
 -neg[-|+] Inverse [don't inverse] the output images (white letters
 on black background, or "night mode"). If -neg+, inverts
 all graphics no matter what. If just -neg, attempts to
 invert text only and not figures. Default = -neg-.
 See also -colorbg and -colorfg.
 -ng  Set gap between notes and main text in the output document.
 The  defaults to inches but can have other units (see
 -h, for example). See -nl and -nr for how to turn on notes
 processing. Default is -ng 0.2.
 -nl[] [,]
 -nr[] [,]
 The source document has notes in the left (-nl) or right
 (-nr) margins. Specific pages can be specified for the
 notes using  (same format as -cbox or -p). If
 , are specified, they specify the
 fraction of the page width where to look for the break
 between the notes and the main page. E.g.
 -nl 0.15,0.25 will look for the boundary between the notes
 and the text between 15%% and 25%% of the way across the
 source page. Use -nl- to turn off all processing of notes
 in the margins (default). Default values for 
 and  are 0.05 to 0.35 for -nl and 0.65 to 0.95
 for -nr.
 Notes in the margins are treated differently than other
 "columns" of text. They will be interspersed with the
 text in the adjacent column of main text.
 Note that -nr... or -nl... will also set -cg to 0.05.
 -nt  Use  parallel threads when OCR-ing a document
 with the Tesseract OCR engine (GOCR is not thread safe).
 This may provide a significant processing speed improvement
 when using Tesseract OCR. Note that a higher number is not
 always faster. You should experiment with your system to
 find the optimum. A negative value is interpreted as a
 percentage of available CPUs. The default is -50, which
 tells k2pdfopt to use half of the available CPU threads.
 Some performances I measured:
 ----------------------------------------------------------
 OCR Speed
 O/S CPU Nthreads improvement
 ----------------------------------------------------------
 Win 10 x64 Core i5 2 (default) 1.5x
 Win 10 x64 Core i5 3 1.6x
 Win 10 x64 Core i5 4 1.8x
 ----------------------------------------------------------
 Win 10 x64 Core i7 2 1.8x
 Win 10 x64 Core i7 3 2.4x
 Win 10 x64 Core i7 4 (default) 2.5x
 Win 10 x64 Core i7 5 2.8x
 Win 10 x64 Core i7 6 2.7x
 Win 10 x64 Core i7 7 2.7x
 Win 10 x64 Core i7 8 2.6x
 ----------------------------------------------------------
 Linux x64 Core i5 2 (default) 1.9x
 Linux x64 Core i5 3 2.6x
 Linux x64 Core i5 4 2.7x
 ----------------------------------------------------------
 Linux x64 Xeon E52690v2 2 1.9x
 Linux x64 Xeon E52690v2 4 3.5x
 Linux x64 Xeon E52690v2 6 5.1x
 Linux x64 Xeon E52690v2 8 6.6x
 Linux x64 Xeon E52690v2 10 (default) 8.7x
 Linux x64 Xeon E52690v2 14 9.5x
 Linux x64 Xeon E52690v2 20 10.2x
 ----------------------------------------------------------
 Interestingly, Linux seems to have much better multithreading
 performance than Windows. I suspect the OS/X results are
 similar to the Linux results.
 NOTE: -nt has no effect if you select -ocrd c or -ocrd p.
 See -ocrd.
 -o  Set the output file name using . %s will be
 replaced with the full name of the source file minus the
 extension. %b will be replaced by the base name of the
 source file minus the extension. %f will be replaced with
 the folder name of the source file. %d will be replaced with
 the source file count (starting with 1). The .pdf extension
 will be appended if you don't specify an extension.
 E.g. -o out%04d.pdf will result in output files out0001.pdf,
 out0002.pdf, ... for the converted files. Def = %s_k2opt
 -------------------------------------------------------------
 BITMAP OUTPUT: For output to bitmaps, you can put -o .png
 or -o .jpg (see -jpeg for quality setting).
 -------------------------------------------------------------
 MORE DETAIL: If  ends in .jpg or .png, the output
 will be in the JPEG or PNG bitmap format, respectively, one
 bitmap per page. If your  has no %d in it, then
 %04d will be appended. If  has only one %d, it will
 get substituted with the page number. If it has two %d's,
 the first will get the file count and the second will get the
 page number. Example: if the source PDF is myfile.pdf, then
 -o %s%03d.png would create myfile001.png, myfile002.png,
 etc., for each page of the PDF.
 -ocr[-] [g|t|m] Attempt [don't attempt] to use optical character
 recognition (OCR) in order to embed searchable text into
 the output PDF document. If followed by t or g, specifies
 the ocr engine to use (tesseract or gocr). If followed by
 m, and if the PDF document has text in it, then the MuPDF
 engine is used to extract the text (sort of a virtual OCR).
 If -ocr is specified with no argument, tesseract is used.
 If tesseract fails (e.g. no language files found), GOCR
 is used. The overall default operation of k2pdfopt is
 -ocr m. See also -ocrvis and -ocrhmax.
 NOTE: Turning on OCR will disable native PDF output.
 DISCLAIMER: The main intent of OCR isn't to improve the
 visual quality of the text at all--at least not the way
 k2pdfopt does it. OCR is most useful on scanned PDFs
 that don't have selectable text to begin with, but using
 OCR with k2pdfopt on such documents doesn't change the
 look of the output PDF file at all. The OCR text is
 simply placed invisibly over the scanned text so that
 you appear to be able to select the scanned text (when,
 in fact, you are selecting the invisibly placed OCR
 text). So the only time you will even notice the OCR
 errors is if you try to search for a word and can't find
 that word because the OCR of that word is incorrect, or
 if you copy a selection of the OCR text and paste it
 into something else so that you can actually see it.
 -ocrcol  If you are simply processing a PDF to OCR it (e.g. if you
 are using the -mode copy option) and the source document has
 multiple columns of text, set this value to the number of
 columns to process (up to 4). Default is to use the same
 value as -col.
 -ocrd w|l|c|p Set OCR detection type for k2pdfopt and Tesseract. 
 can be word (w), line (l), columns (c), or page (p). Default
 is line.
 For -ocrd w, k2pdfopt locates each word in the scanned
 document and passes individual words to Tesseract for
 OCR conversion. This was the only type of detection before
 v2.42 but is not an optimal OCR conversion method when
 using Tesseract.
 For -ocrd l, k2pdfopt passes each line of the converted
 file to Tesseract for conversion. This typically gives
 better results than -ocrd w since Tesseract can better
 determine the text baseline position with a full line.
 For -ocrd c, k2pdfopt detects each column of the converted
 file and passes that to Tesseract for conversion.
 For -ocrd p, k2pdfopt passes the entire output page of text
 to Tesseract and lets Tesseract parse it for word positions.
 Tesseract has done considerable code development for
 detecting words on pages (more than k2pdfopt), so this
 should also be a reliable way to create the OCR layer.
 One drawback to -ocrd c or -ocr p is that there is no benefit
 to using the OCR multithreading option (see -nt).
 -ocrhmax  Set max height for an OCR'd word in inches. Any graphic
 exceeding this height will not be processed with the OCR
 engine. Default = 1.5. See -ocr.
 -ocrlang |? Select the Tesseract OCR Engine language. This is the
 root name of the training data, e.g. -lang eng for English,
 -ocrlang fra for French, -ocrlang chi_sim for simplified
 Chinese. You can also use -l. The default language is
 whatever is in your Tesseract trained data folder. If you
 have more than one .traineddata file in that folder, the
 one with the most recent time stamp is used.
 NOTE 1: As of v2.52, k2pdfopt will download training files
 from github as needed. You can append -fast to the training
 file name to get the fast version, otherwise the best version
 will be downloaded. If the default url fails, you can
 specify the URL (folder name) in the environment variables
 TESSDATA_URL and TESSDATAFAST_URL, e.g.
 set TESSDATA_URL=https://raw.githubusercontent.com/tesseract-ocr/tessdata_best/master
 You will be prompted to approve downloads unless you specify
 the -y command-line option.
 NOTE 2: Use -ocrlang ? to see the list of Tesseract language
 files in your Tesseract data folder and available for
 download.
 NOTE 3: Using the -ocrvis t option will not show the OCR text
 correctly for any character above unicode value 255 since
 k2pdfopt does not use any embedded fonts, but the text
 will convert to the correct Unicode values when copy /
 pasted.
 NOTE 4: Tesseract allows the specification of multiple
 language training files, e.g. -ocrlang eng+fra would
 specify English as the primary and French as the secondary
 OCR language. In practice I have not found this to work
 very well. Try multiple languages in different orders.
 -ocrdpi  Set the desired dpi of the bitmaps passed to the OCR engine
 OR set the desired height of a lower case letter (e.g. 'e')
 in pixels. If  is positive, it is interpreted as dpi.
 If  is negative, the absolute value is interpreted as
 a lowercase letter height in pixels. Any bitmapped text sent
 to the OCR engine will be downsampled (if too large) so that
 the appropriate dpi or lowercase letter size is achieved.
 The default is 300 because I've found this works best
 empirically for Tesseract v4.0.0 English OCR with font sizes
 in the range 8 - 15 pts. Use a lower value if the font size
 in your document is larger than 15 - 20 pts. Or use
 -ocrdpi -24 if you have a wide range of font sizes.
 Use -ocrdpi 0 to disable any downsampling.
 -ocrout[-]  Write [don't write] UTF-8 OCR text output to file
 . See the -o option for more about how
  works. Default extension is .txt. Default is
 no output.
 -ocrsort[-] When a PDF document has its own OCR/Text layer, this option
 orders the OCR text layer by its position on the page. This
 should not be necessary unless the OCR layer was very poorly
 generated. Default is -ocrsort- (off).
 -ocrsp[+|-] When generating the OCR layer, do an entire row of text at
 once, with spaces between each words. By default (-ocrsp-),
 each word is placed separately in the PDF document's OCR
 layer. This causes problems with text selection in some
 readers (for example, individual words cannot be selected).
 Using -ocrsp- may fix behavior like this, but will result in
 less accurate word placement since k2pdfopt does not try to
 exactly match the font used by the document. Use -ocrsp+
 to allow more than one space between each word in the row
 of text in order to optimize the selection position.
 -ocrvbb[-] Verify OCR bounding boxes. For PDF files that have a built-
 in OCR layer, if the resulting text selection does not seem to
 match the graphical word positions in the document, you can
 try this option. It checks the bounding box for each word
 from the OCR layer against the actual graphical placement of
 the word in the document and "shrinks" the bounding box to
 just fit around the word. This only affects non-native PDF
 conversions. Default is -ocrvbb- (turned off).
 -ocrvis  Set OCR visibility flags. Put 's' to show the source doc,
 't' to show the OCR text, and/or 'b' to put a box around
 each word. Default is -ocrvis s. To show both the source
 document and the OCR text overlayed on top: -ocrvis st.
 See also -ocr. See also -ocrlang (the note about -ocrvis t).
 -odpi  Set pixels per inch of output screen (def=167). See also
 -dr, -w, -h, -fc. You can also use -dpi for this.
 See also -fs, -mag.
 -om[b|l|r|t] [][,[units][,...]] Set the blank area margins
 on the output device. Works very much like the -m option.
 See -m for more about the syntax. Default = 0.02 inches.
 Note that the 's', 't', and 'x' units for -om all behave
 the same and scale to the device size. E.g. -om 0.1s will
 make the device screen margins 0.1 times the device width
 (for the left and right margins) or height (for the top and
 bottom margins) of the output device screen.
 -ow[-|+] [] Set the minimum file size (in MB) where overwriting the
 file will not be done without prompting. Set to -1 (or
 just -ow with no value) to overwrite all files with no
 prompting. Set to 0 (or just -ow-) to prompt for any
 overwritten file. Def = -ow 10 (any existing file
 over 10 MB will not be overwritten without prompting).
 Use the + option (-ow+) to rename the existing file
 instead of overwriting it. Existing files will be renamed
 as follows:
 file_k2pdfopt.pdf --> file_k2pdfopt_old.pdf
 See also -y option.
 -p  Specify pages to convert.  must not have any
 spaces. E.g. -p 1-3,5,9,10- would do pages 1 through 3,
 page 5, page 9, and pages 10 through the end. The letters
 'e' and 'o' can be used to denote even and odd pages, e.g.
 -p o,e Process all odd pages, then all even ones.
 -p 2-52e,3-33o Process 2,4,6,...,52,3,5,7,...,33.
 Overridden by -px option. See -px.
 -pad  A shortcut for -pl, -pt, -pr, -pb. E.g. -pad 15,10,13,20
 is the same as -pl 15 -pt 10 -pr 13 -pb 20. Also, using
 -pad 15 will set all pads to 15, for example.
 -p[b|l|r|t]  Pad [bottom|left|right|top] side of destination bitmap with
  rows. Defaults = 4 (bottom), 0 (left), 3 (right), and
 0 (top). Example: -pb 10. This is typically only used on
 certain devices to get the page to come out just right. For
 setting margins on the output device, use -om. See also -pad.
 -png (Default) Use PNG compression in PDF file. See also -jpeg.
 -ppgs[-] Post process [do not post process] with ghostscript. This
 will take the final PDF output and process it using
 ghostscript's pdfwrite device (assuming ghostscript is
 available). A benefit to doing this is that all "invisible"
 and/or overlapping text regions (outside cropping areas) get
 completely removed, so that text selection capability is
 improved. The actual ghostscript command used is:
 gs -dSAFER -dBATCH -q -dNOPAUSE -sDEVICE=pdfwrite
 -dPDFSETTINGS=/prepress -sOutputFile=
 
 The default is not to post process with ghostscript.
 -px  Exclude pages from . Overrides -p option. Default
 is no excluded pages (-px -1).
 -r[-] Right-to-left [left-to-right] page scans. Default is
 left to right. See also -go option.
 -rhmin  Row Height Minimum. This sets the minimum height that any
 text row or text-row-like object can be, in points. If
 the object is less than this height, it will be ignored
 in the converted file for the processes of formatting.
 The default is -1 (which means it is not used).
 This is an experimental option (as of v2.52).
 -rls[+|-] Restore [+] or don't restore [-] the last command-line
 settings from the environment variable K2PDFOPT_CUSTOM0.
 The default (-rls) is to restore the settings if there are no
 other command-line options specified when running (from.
 either the command line or the K2PDFOPT env var.), unless
 those options are "-gui" or specify a file name.
 -rsf  Row Split Figure of merit (expert mode). After k2pdfopt has
 looked for gaps between rows of text, it will check to see
 if there appear to be missed gaps (e.g. if one row is twice
 the height of all the others). Increasing this value makes
 it harder for k2pdfopt to split a row. Lowering it makes it
 easier. Default value = 20.
 -rt |auto[+]|aep Rotate source page counterclockwise by  degrees.
 NOTE: If you're trying to get "landscape" output so that
 you can turn your reader on its side, use -ls instead of
 -rt. The -rt option is intended to be used for when your
 source PDF is incorrectly rotated--e.g. if you view it on
 a standard PC reader and it comes up sideways.
  can be 90, 180, 270. Or use "-rt auto" to examine up
 to 10 pages of each file to determine the orientation used
 on the entire file (this is the default). Or use "-rt aep"
 to auto-detect the rotation of every page. If you have
 different pages that are rotated differently from each other
 within one file, you can use this option to try to auto-
 rotate each source page. Use -rt auto+ to turn on auto-
 detect even in preview mode (otherwise it is off).
 See also -ls.
 -s[-] Sharpen [don't sharpen] images. Default is to sharpen.
 -sm[-] Show [don't show] marked source. This is a debugging tool
 where k2pdfopt will mark the source file with the regions it
 finds on them and the order in which it processes them and
 save it as _marked.pdf. Default is not to show
 marked source. Red regions are found on the first pass
 (use -f2p -2 to put each red region on a separate page).
 Green lines mark vertical regions affected by -vb and -vs.
 Gray lines mark individual rows of text (top, bottom, and
 baseline). Blue boxes show individual words (passed to OCR
 if -ocr is specified).
 -sp[-] For each file on the command-line, just echo the number
 of pages--don't process. Default = off (-sp-).
 -t[-] Trim [don't trim] the white space from around the edges of
 any output region. Default is to trim. Using -t- is not
 recommended unless you want to exactly duplicate the source
 document.
 -title