java Buffered Image：检测黑色像素

问题描述

我有这个简单的代码通过24位彩色windows bmp文件

I have this simple code to go through a 24bit color windows bmp file

BufferedImage mapa = BMPDecoder.read(new File("maps/map.bmp"));

final int xmin = mapa.getMinX();
final int ymin = mapa.getMinY();

final int ymax = ymin + mapa.getHeight();
final int xmax = xmin + mapa.getWidth();


for (int i = xmin;i<xmax;i++)
{
   for (int j = ymin;j<ymax;j++)
   {

    int pixel = mapa.getRGB(i, j);

    if (pixel == 0)
    {
        System.out.println("black at "+i+","+j);
    }
   }
}

然而，当测试时完全黑色的图像，我得到像素的这个值： -16777216 。

However, when testing on a completely black image, I get this value at pixel : -16777216.

我希望得到一个0x0。

I was hoping to get a 0x0.

我如何测试黑色像素（或任何其他颜色）？

How can I test for black pixels (or any other color for that reason) ?

我正在测试（（像素& 0xff）== 0）。这是正确的吗？
提前致谢。

Im testing against ((pixel & 0xff) == 0). Is this right?Thanks in advance.

推荐答案

-16777216 是 0xFF000000 十六进制，对应于不透明的黑色。

-16777216 is 0xFF000000 in hexadecimal, corresponding to opaque black.

附录：看看你的更新，我想你想要（（像素& 0x00FFFFFF）== 0）作为您的谓词。

Addendum: Looking at your update, I'd think you want ((pixel & 0x00FFFFFF) == 0) as your predicate.

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