这篇将讲到图片特效处理的图片叠加效果。跟前面一样是对像素点进行处理，可参照前面的和两篇文章，此篇所讲的与之前有一点区别。叠加原理是两张图片的像素点按透明度叠加，不会进行颜色过滤。叠加图片可以是JPG格式，跟前在一样，最好是放大assets目录。下面看效果图：

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代码：

/**  * 图片效果叠加  * @param bmp 限制了尺寸大小的Bitmap  * @return  */ private Bitmap overlay(Bitmap bmp) {  long start = System.currentTimeMillis();  int width = bmp.getWidth();  int height = bmp.getHeight();  Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);    // 对边框图片进行缩放  Bitmap overlay = BitmapFactory.decodeResource(mContext.getResources(), R.drawable.rainbow_overlay);  int w = overlay.getWidth();  int h = overlay.getHeight();  float scaleX = width * 1F / w;  float scaleY = height * 1F / h;  Matrix matrix = new Matrix();  matrix.postScale(scaleX, scaleY);    Bitmap overlayCopy = Bitmap.createBitmap(overlay, 0, 0, w, h, matrix, true);    int pixColor = 0;  int layColor = 0;    int pixR = 0;  int pixG = 0;  int pixB = 0;  int pixA = 0;    int newR = 0;  int newG = 0;  int newB = 0;  int newA = 0;    int layR = 0;  int layG = 0;  int layB = 0;  int layA = 0;    final float alpha = 0.5F;    int[] srcPixels = new int[width * height];  int[] layPixels = new int[width * height];  bmp.getPixels(srcPixels, 0, width, 0, 0, width, height);  overlayCopy.getPixels(layPixels, 0, width, 0, 0, width, height);    int pos = 0;  for (int i = 0; i < height; i++)  {   for (int k = 0; k < width; k++)   {    pos = i * width + k;    pixColor = srcPixels[pos];    layColor = layPixels[pos];        pixR = Color.red(pixColor);    pixG = Color.green(pixColor);    pixB = Color.blue(pixColor);    pixA = Color.alpha(pixColor);        layR = Color.red(layColor);    layG = Color.green(layColor);    layB = Color.blue(layColor);    layA = Color.alpha(layColor);        newR = (int) (pixR * alpha + layR * (1 - alpha));    newG = (int) (pixG * alpha + layG * (1 - alpha));    newB = (int) (pixB * alpha + layB * (1 - alpha));    layA = (int) (pixA * alpha + layA * (1 - alpha));        newR = Math.min(255, Math.max(0, newR));    newG = Math.min(255, Math.max(0, newG));    newB = Math.min(255, Math.max(0, newB));    newA = Math.min(255, Math.max(0, layA));        srcPixels[pos] = Color.argb(newA, newR, newG, newB);   }  }    bitmap.setPixels(srcPixels, 0, width, 0, 0, width, height);  long end = System.currentTimeMillis();  Log.d("may", "overlayAmeliorate used time="+(end - start));  return bitmap; }