Android开发：轻松实现图片倒影效果

效果如下：

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2011-12-11 09:46 上传

 

主要代码如下：

1. public static Bitmap createReflectedImage(Bitmap originalImage) {
2. final int reflectionGap = 4;
3. int width = originalImage.getWidth();
4. int height = originalImage.getHeight();
5. Matrix matrix = new Matrix();
6. matrix.preScale(1, -1);
7. Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0,
8. height / 2, width, height / 2, matrix, false);
9. Bitmap bitmapWithReflection = Bitmap.createBitmap(width,
10. (height + height / 2), Config.ARGB_8888);
11. Canvas canvas = new Canvas(bitmapWithReflection);
12. canvas.drawBitmap(originalImage, 0, 0, null);
13. Paint defaultPaint = new Paint();
14. canvas.drawRect(0, height, width, height + reflectionGap,
    defaultPaint);
15. canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);
16. Paint paint = new Paint();
17. LinearGradient shader = new LinearGradient(0,
18. originalImage.getHeight(), 0, bitmapWithReflection.getHeight()
19. + reflectionGap, 0×70ffffff, 0×00ffffff,
20. TileMode.MIRROR);
21. paint.setShader(shader);
22. paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
23. canvas.drawRect(0, height, width, bitmapWithReflection.getHeight()
24. + reflectionGap, paint);
25. return bitmapWithReflection;
26. }

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解释一下：

1. Matrix matrix = new Matrix();
2. matrix.preScale(1, -1);

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实现图片的反转，见Android利用Matrix简单处理图片。

1. Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0,
2. height / 2, width, height / 2, matrix,
   false);

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创建反转后的图片Bitmap对象，图片高是原图的一半。

1. Bitmap bitmapWithReflection = Bitmap.createBitmap(width,
2. (height + height / 2), Config.ARGB_8888);

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创建标准的Bitmap对象，宽和原图一致，高是原图的1.5倍。

1. Canvas canvas = new Canvas(bitmapWithReflection);
2. canvas.drawBitmap(originalImage, 0, 0, null);

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创建画布对象，将原图画于画布，起点是原点位置。

1. Paint defaultPaint = new Paint();
2. canvas.drawRect(0, height, width, height + reflectionGap,
   defaultPaint);
3. canvas.drawBitmap(reflectionImage, 0, height + reflectionGap,
   null);

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将反转后的图片画到画布中。

1. LinearGradient shader = new LinearGradient(0,
2. originalImage.getHeight(), 0, bitmapWithReflection.getHeight()
3. + reflectionGap, 0×70ffffff, 0×00ffffff,

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创建线性渐变LinearGradient 对象。

1. canvas.drawRect(0, height, width, bitmapWithReflection.getHeight()
2. + reflectionGap, paint);

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画布画出反转图片大小区域，然后把渐变效果加到其中，就出现了图片的倒影效果。