Android CreateBitmap
public class CreateBitmap extends Activity{ @Override protected void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onCreate(savedInstanceState); setContentView(new SampleView(this)); } private class SampleView extends View{ private Bitmap[] mBitmaps; private Bitmap[] mJPEGs; private Bitmap[] mPNGs; private int[] mColors; private Paint mPaint; private static final int WIDTH=50; private static final int HEIGHT=50; private static final int STRIDE=64;//must be >=WIDTH public SampleView(Context context) { super(context); setFocusable(true); mColors=initColors(); mBitmaps=new Bitmap[6]; mPaint=new Paint(); mPaint.setDither(true); //these three are initialized with colors[] mBitmaps[0]=Bitmap.createBitmap(mColors, 0, STRIDE, WIDTH, HEIGHT, Config.ARGB_8888); mBitmaps[1]=Bitmap.createBitmap(mColors, 0, STRIDE, WIDTH, HEIGHT, Config.RGB_565); mBitmaps[2]=Bitmap.createBitmap(mColors, 0, STRIDE, WIDTH, HEIGHT, Config.ARGB_4444); //these three will have their colors[] set later. mBitmaps[3]=Bitmap.createBitmap(WIDTH, HEIGHT, Config.ARGB_8888); mBitmaps[4]=Bitmap.createBitmap(WIDTH, HEIGHT, Config.RGB_565); mBitmaps[5]=Bitmap.createBitmap(WIDTH, HEIGHT, Config.ARGB_4444); for (int i = 3; i <=5; i++) { mBitmaps[i].setPixels(mColors, 0, STRIDE, 0, 0, WIDTH, HEIGHT); } //now decode/encode using JPEG and PNG mJPEGs=new Bitmap[mBitmaps.length]; mPNGs=new Bitmap[mBitmaps.length]; for (int i = 0; i < mBitmaps.length; i++) { mJPEGs[i]=codec(mBitmaps[i],Bitmap.CompressFormat.JPEG,80); mPNGs[i]=codec(mBitmaps[i],Bitmap.CompressFormat.PNG,0); } } @Override protected void onDraw(Canvas canvas) { // TODO Auto-generated method stub super.onDraw(canvas); canvas.drawColor(Color.WHITE); for (int i = 0; i < mBitmaps.length; i++) { canvas.drawBitmap(mBitmaps[i], 0, 0, null); canvas.drawBitmap(mJPEGs[i], 80,0, null); canvas.drawBitmap(mPNGs[i], 160, 0, null); canvas.translate(0, mBitmaps[i].getHeight()); } //draw the color array directly,w/o(without) creating a bitmap object canvas.drawBitmap(mColors, 0, STRIDE, 0, 0, WIDTH, HEIGHT, true, null); canvas.translate(0, HEIGHT); canvas.drawBitmap(mColors, 0, STRIDE, 0, 0, WIDTH, HEIGHT, true, mPaint); } private Bitmap codec(Bitmap bitmap, CompressFormat format, int quality) { ByteArrayOutputStream baos=new ByteArrayOutputStream(); bitmap.compress(format, quality, baos); byte[] data=baos.toByteArray(); return BitmapFactory.decodeByteArray(data, 0, data.length); } private int[] initColors() { int[] colors=new int[STRIDE*HEIGHT]; for (int y = 0; y < HEIGHT; y++) {//use of x,y is legible then the use of i,j for (int x = 0; x < WIDTH; x++) { int r = x * 255 / (WIDTH - 1); int g = y * 255 / (HEIGHT - 1); int b = 255 - Math.min(r, g); int a = Math.max(r, g); colors[y*STRIDE+x]=(a<<24)|(r<<16)|(g<<8)|(b);//the shift operation generates the color ARGB } } return colors; } } }
Bitmap中setPiexls的解释：
public void setPixels (int[] pixels, int offset, int stride, int x, int y, int width, int height)
Replace pixels in the bitmap with the colors in the array. Each element in the array is a packed int prepresenting a Color
Parameters
| pixels | The colors to write to the bitmap |
|---|---|
| offset | The index of the first color to read from pixels[] |
| stride | The number of colors in pixels[] to skip between rows. Normally this value will be the same as the width of the bitmap, but it can be larger (or negative). |
| x | The x coordinate of the first pixel to write to in the bitmap. |
| y | The y coordinate of the first pixel to write to in the bitmap. |
| width | The number of colors to copy from pixels[] per row |
| height | The number of rows to write to the bitmap |
Throws
| IllegalStateException | if the bitmap is not mutable |
|---|---|
| IllegalArgumentException | if x, y, width, height are outside of the bitmap's bounds. |
| ArrayIndexOutOfBoundsException | if the pixels array is too small to receive the specified number of pixels. |