学步园

public class CreateBitmap extends Activity{<br /> @Override<br /> protected void onCreate(Bundle savedInstanceState) {<br /> // TODO Auto-generated method stub<br /> super.onCreate(savedInstanceState);<br /> setContentView(new SampleView(this));<br /> }</p> <p> private class SampleView extends View{<br /> private Bitmap[] mBitmaps;<br /> private Bitmap[] mJPEGs;<br /> private Bitmap[] mPNGs;<br /> private int[] mColors;<br /> private Paint mPaint;</p> <p> private static final int WIDTH=50;<br /> private static final int HEIGHT=50;<br /> private static final int STRIDE=64;//must be >=WIDTH<br /> public SampleView(Context context) {<br /> super(context);<br /> setFocusable(true);</p> <p> mColors=initColors();<br /> mBitmaps=new Bitmap[6];<br /> mPaint=new Paint();<br /> mPaint.setDither(true);</p> <p> //these three are initialized with colors[]<br /> mBitmaps[0]=Bitmap.createBitmap(mColors, 0, STRIDE, WIDTH, HEIGHT, Config.ARGB_8888);<br /> mBitmaps[1]=Bitmap.createBitmap(mColors, 0, STRIDE, WIDTH, HEIGHT, Config.RGB_565);<br /> mBitmaps[2]=Bitmap.createBitmap(mColors, 0, STRIDE, WIDTH, HEIGHT, Config.ARGB_4444);</p> <p> //these three will have their colors[] set later.<br /> mBitmaps[3]=Bitmap.createBitmap(WIDTH, HEIGHT, Config.ARGB_8888);<br /> mBitmaps[4]=Bitmap.createBitmap(WIDTH, HEIGHT, Config.RGB_565);<br /> mBitmaps[5]=Bitmap.createBitmap(WIDTH, HEIGHT, Config.ARGB_4444);</p> <p> for (int i = 3; i <=5; i++) {<br /> mBitmaps[i].setPixels(mColors, 0, STRIDE, 0, 0, WIDTH, HEIGHT);<br /> }</p> <p> //now decode/encode using JPEG and PNG<br /> mJPEGs=new Bitmap[mBitmaps.length];<br /> mPNGs=new Bitmap[mBitmaps.length];<br /> for (int i = 0; i < mBitmaps.length; i++) {<br /> mJPEGs[i]=codec(mBitmaps[i],Bitmap.CompressFormat.JPEG,80);<br /> mPNGs[i]=codec(mBitmaps[i],Bitmap.CompressFormat.PNG,0);<br /> }<br /> }</p> <p> @Override<br /> protected void onDraw(Canvas canvas) {<br /> // TODO Auto-generated method stub<br /> super.onDraw(canvas);<br /> canvas.drawColor(Color.WHITE);</p> <p> for (int i = 0; i < mBitmaps.length; i++) {<br /> canvas.drawBitmap(mBitmaps[i], 0, 0, null);<br /> canvas.drawBitmap(mJPEGs[i], 80,0, null);<br /> canvas.drawBitmap(mPNGs[i], 160, 0, null);<br /> canvas.translate(0, mBitmaps[i].getHeight());<br /> }</p> <p> //draw the color array directly,w/o(without) creating a bitmap object<br /> canvas.drawBitmap(mColors, 0, STRIDE, 0, 0, WIDTH, HEIGHT, true, null);<br /> canvas.translate(0, HEIGHT);<br /> canvas.drawBitmap(mColors, 0, STRIDE, 0, 0, WIDTH, HEIGHT, true, mPaint);<br /> }<br /> private Bitmap codec(Bitmap bitmap, CompressFormat format, int quality) {<br /> ByteArrayOutputStream baos=new ByteArrayOutputStream();<br /> bitmap.compress(format, quality, baos);<br /> byte[] data=baos.toByteArray();<br /> return BitmapFactory.decodeByteArray(data, 0, data.length);<br /> }<br /> private int[] initColors() {<br /> int[] colors=new int[STRIDE*HEIGHT];<br /> for (int y = 0; y < HEIGHT; y++) {//use of x,y is legible then the use of i,j<br /> for (int x = 0; x < WIDTH; x++) {<br /> int r = x * 255 / (WIDTH - 1);<br /> int g = y * 255 / (HEIGHT - 1);<br /> int b = 255 - Math.min(r, g);<br /> int a = Math.max(r, g);<br /> colors[y*STRIDE+x]=(a<<24)|(r<<16)|(g<<8)|(b);//the shift operation generates the color ARGB<br /> }<br /> }<br /> return colors;<br /> }</p> <p> }<br /> }<br />  

Bitmap中setPiexls的解释：

public void setPixels (int[] pixels, int offset, int stride, int x, int y, int width, int height)