The file containing the source code shown below is located in the corresponding directory in <sdk>/samples/android-<version>/...
/*
* Copyright (C) 2007 The Android开源工程
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.android.apis.graphics;
import android.content.Context;
import android.graphics.*;
import android.os.Bundle;
import android.view.*;
import java.nio.IntBuffer;
import java.nio.ShortBuffer;
public class BitmapPixels extends GraphicsActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new SampleView(this));
}
private static class SampleView extends View {
private Bitmap mBitmap1;
private Bitmap mBitmap2;
private Bitmap mBitmap3;
// access the red component from a premultiplied color
private static int getR32(int c) { return (c >> 0) & 0xFF; }
// access the red component from a premultiplied color
private static int getG32(int c) { return (c >> 8) & 0xFF; }
// access the red component from a premultiplied color
private static int getB32(int c) { return (c >> 16) & 0xFF; }
// access the red component from a premultiplied color
private static int getA32(int c) { return (c >> 24) & 0xFF; }
/**
* This takes components that are already in premultiplied form, and
* packs them into an int in the correct device order.
*/
private static int pack8888(int r, int g, int b, int a) {
return (r << 0) | ( g << 8) | (b << 16) | (a << 24);
}
private static short pack565(int r, int g, int b) {
return (short)((r << 11) | ( g << 5) | (b << 0));
}
private static short pack4444(int r, int g, int b, int a) {
return (short)((a << 0) | ( b << 4) | (g << 8) | (r << 12));
}
private static int mul255(int c, int a) {
int prod = c * a + 128;
return (prod + (prod >> 8)) >> 8;
}
/**
* Turn a color int into a premultiplied device color
*/
private static int premultiplyColor(int c) {
int r = Color.red(c);
int g = Color.green(c);
int b = Color.blue(c);
int a = Color.alpha(c);
// now apply the alpha to r, g, b
r = mul255(r, a);
g = mul255(g, a);
b = mul255(b, a);
// now pack it in the correct order
return pack8888(r, g, b, a);
}
private static void makeRamp(int from, int to, int n,
int[] ramp8888, short[] ramp565,
short[] ramp4444) {
int r = getR32(from) << 23;
int g = getG32(from) << 23;
int b = getB32(from) << 23;
int a = getA32(from) << 23;
// now compute our step amounts per componenet (biased by 23 bits)
int dr = ((getR32(to) << 23) - r) / (n - 1);
int dg = ((getG32(to) << 23) - g) / (n - 1);
int db = ((getB32(to) << 23) - b) / (n - 1);
int da = ((getA32(to) << 23) - a) / (n - 1);
for (int i = 0; i < n; i++) {
ramp8888[i] = pack8888(r >> 23, g >> 23, b >> 23, a >> 23);
ramp565[i] = pack565(r >> (23+3), g >> (23+2), b >> (23+3));
ramp4444[i] = pack4444(r >> (23+4), g >> (23+4), b >> (23+4),
a >> (23+4));
r += dr;
g += dg;
b += db;
a += da;
}
}
private static IntBuffer makeBuffer(int[] src, int n) {
IntBuffer dst = IntBuffer.allocate(n*n);
for (int i = 0; i < n; i++) {
dst.put(src);
}
dst.rewind();
return dst;
}
private static ShortBuffer makeBuffer(short[] src, int n) {
ShortBuffer dst = ShortBuffer.allocate(n*n);
for (int i = 0; i < n; i++) {
dst.put(src);
}
dst.rewind();
return dst;
}
public SampleView(Context context) {
super(context);
setFocusable(true);
final int N = 100;
int[] data8888 = new int[N];
short[] data565 = new short[N];
short[] data4444 = new short[N];
makeRamp(premultiplyColor(Color.RED), premultiplyColor(Color.GREEN),
N, data8888, data565, data4444);
mBitmap1 = Bitmap.createBitmap(N, N, Bitmap.Config.ARGB_8888);
mBitmap2 = Bitmap.createBitmap(N, N, Bitmap.Config.RGB_565);
mBitmap3 = Bitmap.createBitmap(N, N, Bitmap.Config.ARGB_4444);
mBitmap1.copyPixelsFromBuffer(makeBuffer(data8888, N));
mBitmap2.copyPixelsFromBuffer(makeBuffer(data565, N));
mBitmap3.copyPixelsFromBuffer(makeBuffer(data4444, N));
}
@Override protected void onDraw(Canvas canvas) {
canvas.drawColor(0xFFCCCCCC);
int y = 10;
canvas.drawBitmap(mBitmap1, 10, y, null);
y += mBitmap1.getHeight() + 10;
canvas.drawBitmap(mBitmap2, 10, y, null);
y += mBitmap2.getHeight() + 10;
canvas.drawBitmap(mBitmap3, 10, y, null);
}
}
}