ImageView

Android的ImageView控件。

ImageView.ScaleType

1. center

   Center the image in the view, but perform no scaling. 

2. center_crop

   Scale the image uniformly (maintain the image's aspect ratio) so that both dimensions (width and height) of the image will be equal to or larger than the corresponding dimension of the view (minus padding). The image is then centered in the view.

3. center_inside

   Scale the image uniformly (maintain the image's aspect ratio) so that both dimensions (width and height) of the image will be equal to or less than the corresponding dimension of the view (minus padding). The image is then centered in the view.

4. fit_center

   Scale the image using CENTER.

5. fit_end

   Scale the image using END.

6. fit_start

   Scale the image using START.

7. fit_xy

   Scale the image using FILL.

8. matrix

   Scale using the image matrix when drawing. The image matrix can be set using setImageMatrix(Matrix).

上面说到的center、end、start、fill属性都在Matrix.ScaleToFit里。

Matrix.ScaleToFit

1、center

Compute a scale that will maintain the original src aspect ratio, but will also ensure that src fits entirely inside dst.

2、end

Compute a scale that will maintain the original src aspect ratio, but will also ensure that src fits entirely inside dst.

3、start

Compute a scale that will maintain the original src aspect ratio, but will also ensure that src fits entirely inside dst.

4、fill

Scale in X and Y independently, so that src matches dst exactly.

资料

1. 如何缩放图片并保持宽高比http://stackoverflow.com/questions/2521959/how-to-scale-an-image-in-imageview-to-keep-the-aspect-ratio