如何在具有透明度的 java BufferedImage 中读取像素颜色 [英] How to read pixel color in a java BufferedImage with transparency

问题描述

我正在按如下方式读取 BufferedImage 中的像素颜色:

I am reading pixel color in a BufferedImage as follows:

.....
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;

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.

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.

如何检测像素实际上是透明的而不是彩色的?

How do I detect that the pixel is actually transparent and not colored?

谢谢

推荐答案

int alpha = (colour>>24) & 0xff;

结果也是一个从 0(完全透明)到 255(完全不透明)的值.

The result is also a value ranging from 0 (completely transparent) to 255 (completely opaque).

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