如何在具有透明度的 java BufferedImage 中读取像素颜色
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How to read pixel color in a java BufferedImage with transparency
提问by Richard H
I am reading pixel color in a BufferedImage as follows:
我正在读取 BufferedImage 中的像素颜色，如下所示：
.....
InputStream is = new BufferedInputStream(conn.getInputStream());
BufferedImage image = ImageIO.read(is);
int color = image.getRGB(x, y);
int red = (colour & 0x00ff0000) >> 16;
int green = (colour & 0x0000ff00) >> 8;
int blue = colour & 0x000000ff;
Now this works fine except for png's with transparency. I find that if x,y refer to a transparent pixel with no color, i still read a color, generally the same color as used elsewhere in the image.
现在这工作正常，除了透明的 png。我发现如果 x,y 指的是一个没有颜色的透明像素，我仍然会读取一种颜色，通常与图像中其他地方使用的颜色相同。
How do I detect that the pixel is actually transparent and not colored?
如何检测像素实际上是透明的而不是彩色的？
Thanks
谢谢
采纳答案by jarnbjo
int alpha = (colour>>24) & 0xff;
The result is also a value ranging from 0 (completely transparent) to 255 (completely opaque).
结果也是一个范围从 0（完全透明）到 255（完全不透明）的值。
