如何生成带倒影的Bitmap【转】

public static Bitmap createReflectedImage(Context context, Bitmap originalImage) { 
                   //The gap we want between the reflection and the original image 
                   final int reflectionGap = 4; 
                    
                        int width = originalImage.getWidth();
                        int height = originalImage.getHeight();
                         
                   
                        //This will not scale but will flip on the Y axis
                        Matrix matrix = new Matrix();
                        matrix.preScale(1, -1);
                         
                        //Create a Bitmap with the flip matrix applied to it.
                        //We only want the bottom half of the image
                        Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0, height/2, width, height/2, matrix, false);
                         
                             
                        //Create a new bitmap with same width but taller to fit reflection
                        Bitmap bitmapWithReflection = Bitmap.createBitmap(width
                          , (height + height/2), Config.ARGB_8888);
                       
                       //Create a new Canvas with the bitmap that's big enough for
                       //the image plus gap plus reflection
                       Canvas canvas = new Canvas(bitmapWithReflection);
                       //Draw in the original image
                       canvas.drawBitmap(originalImage, 0, 0, null);
                       //Draw in the gap
                       Paint defaultPaint = new Paint();
                       canvas.drawRect(0, height, width, height + reflectionGap, defaultPaint);
                       //Draw in the reflection
                       canvas.drawBitmap(reflectionImage,0, height + reflectionGap, null);
                        
                       //Create a shader that is a linear gradient that covers the reflection
                       Paint paint = new Paint();
                       LinearGradient shader = new LinearGradient(0, originalImage.getHeight(), 0,
                         bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff, 0x00ffffff,
                         TileMode.CLAMP);
                      //Set the paint to use this shader (linear gradient)
                       paint.setShader(shader);
                       //Set the Transfer mode to be porter duff and destination in
                       paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
                       //Draw a rectangle using the paint with our linear gradient
                       canvas.drawRect(0, height, width,
                       bitmapWithReflection.getHeight() + reflectionGap, paint);
                       
                   return bitmapWithReflection;
           }