android图片特效处理之图片叠加

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。