android图片特效处理之图片叠加

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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android图像处理系列之七－－图片涂鸦，水印－图片叠加和android图像处理系列之六－－给图片添加边框（下）－图片叠加两篇文章，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;          }

叠加的边框图片还是大点比较好，也要控制被叠加图片大小。alpha变量值可以根据需求修改，建议还是大于0.5比较好，不然原图会看不清楚。

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