在 Java 中自动裁剪图像的白色边框_java 裁剪白色像素

在业务场景中是要在前端中用Javascript来实现这个功能，如果在后端实现也不是不可以，所以网上搜索了一番，但是最后没有尝试和采用这种方法（用了一种很low的方法），在此记录一下，日后再用到类似的可以翻出来看看。

裁剪所有 4 个边的方法，使用最左上角像素的颜色作为基线，并允许颜色变化的容差，这样图像中的噪声就不会使裁剪变得无用

public BufferedImage getCroppedImage(BufferedImage source, double tolerance) {
   // Get our top-left pixel color as our "baseline" for cropping
   int baseColor = source.getRGB(0, 0);
   int width = source.getWidth();
   int height = source.getHeight();

   int topY = Integer.MAX_VALUE, topX = Integer.MAX_VALUE;
   int bottomY = -1, bottomX = -1;
   for(int y=0; y<height; y++) {
      for(int x=0; x<width; x++) {
         if (colorWithinTolerance(baseColor, source.getRGB(x, y), tolerance)) {
            if (x < topX) topX = x;
            if (y < topY) topY = y;
            if (x > bottomX) bottomX = x;
            if (y > bottomY) bottomY = y;
         }
      }
   }
   BufferedImage destination = new BufferedImage( (bottomX-topX+1), 
                 (bottomY-topY+1), BufferedImage.TYPE_INT_ARGB);
   destination.getGraphics().drawImage(source, 0, 0, 
               destination.getWidth(), destination.getHeight(), 
               topX, topY, bottomX, bottomY, null);
   return destination;
}

private boolean colorWithinTolerance(int a, int b, double tolerance) {
    int aAlpha  = (int)((a & 0xFF000000) >>> 24);   // Alpha level
    int aRed    = (int)((a & 0x00FF0000) >>> 16);   // Red level
    int aGreen  = (int)((a & 0x0000FF00) >>> 8);    // Green level
    int aBlue   = (int)(a & 0x000000FF);            // Blue level

    int bAlpha  = (int)((b & 0xFF000000) >>> 24);   // Alpha level
    int bRed    = (int)((b & 0x00FF0000) >>> 16);   // Red level
    int bGreen  = (int)((b & 0x0000FF00) >>> 8);    // Green level
    int bBlue   = (int)(b & 0x000000FF);            // Blue level

    double distance = Math.sqrt((aAlpha-bAlpha)*(aAlpha-bAlpha) +
                                (aRed-bRed)*(aRed-bRed) +
                                (aGreen-bGreen)*(aGreen-bGreen) +
                                (aBlue-bBlue)*(aBlue-bBlue));
    // 510.0 is the maximum distance between two colors 
    // (0,0,0,0 -> 255,255,255,255)
    double percentAway = distance / 510.0d;     
    return (percentAway > tolerance);
}
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原文链接