为什么在Java中缩小后图像看起来很糟糕？ [英] Why does this image look so bad after being scaled down in Java?

问题描述

以下是原始图片： http://rank.my/public/ images / uploaded / orig-4193395691714613396.png

此处缩小至300x225：

http://rank.my/public/images/uploaded/norm-4193395691714613396 .png

此处缩小至150x112：

http://rank.my/public/images/uploaded/small-4193395691714613396.png

正如您所看到的，300x225看起来非常糟糕，而150x112看起来很糟糕。这里是我用来缩小图像的代码：

  private static BufferedImage createResizedCopy（final BufferedImage source，final int destWidth ，
 final int destHeight）{
 final BufferedImage resized = new BufferedImage（destWidth，destHeight，source.getType（））; 
 final Graphics2D bg = resized.createGraphics（）; 
 bg.setRenderingHint（RenderingHints.KEY_INTERPOLATION，RenderingHints.VALUE_INTERPOLATION_BILINEAR）; 
 bg.setRenderingHint（RenderingHints.KEY_RENDERING，RenderingHints.VALUE_RENDER_QUALITY）; 
 bg.setRenderingHint（RenderingHints.KEY_ANTIALIASING，RenderingHints.VALUE_ANTIALIAS_ON）; 
 final float sx =（float）destWidth / source.getWidth（）; 
 final float sy =（float）destHeight / source.getHeight（）; 
 bg.scale（sx，sy）; 
 bg.drawImage（source，0，0，null）; 
 bg.dispose（）; 
返回调整大小; 
} 
  

我在这里做错了什么？图像缩放不一定要特别快，质量绝对是速度优先。我是否使用了错误的技术？

解决方案

有三种方法可以解决缩小问题。首先是分多步进行，每步减少不超过75％。第二种是在调整大小之前模糊图像;它越缩小，你越需要模糊。第三种方法是使用一种方法，该方法使用多于2×2到4×4像素块进行过滤，这些像素块是由朴素双线性或双三次插值方法使用的。随着收缩因子变大，过滤器使用的像素块也应该变大，否则会出现锯齿伪像，如您在此处看到的那样。

Here is the original image: http://rank.my/public/images/uploaded/orig-4193395691714613396.png

And here it is scaled down to 300x225:

http://rank.my/public/images/uploaded/norm-4193395691714613396.png

And here it is scaled down to 150x112:

http://rank.my/public/images/uploaded/small-4193395691714613396.png

As you can see, 300x225 looks pretty bad, and 150x112 looks awful. Here is the code I'm using to scale down the image:

private static BufferedImage createResizedCopy(final BufferedImage source, final int destWidth,
        final int destHeight) {
    final BufferedImage resized = new BufferedImage(destWidth, destHeight, source.getType());
    final Graphics2D bg = resized.createGraphics();
    bg.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
    bg.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
    bg.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    final float sx = (float) destWidth / source.getWidth();
    final float sy = (float) destHeight / source.getHeight();
    bg.scale(sx, sy);
    bg.drawImage(source, 0, 0, null);
    bg.dispose();
    return resized;
}

What am I doing wrong here? The image scaling doesn't have to be especially fast, quality is definitely a priority over speed. Am I using the wrong technique?

解决方案

There are three ways to fix the downscaling problem. First is to do it in multiple steps, with no more than a 75% reduction in each step. The second is to blur the image before resizing; the more it shrinks, the more you'll have to blur. The third way is to use a method that filters using more than the 2x2 to 4x4 pixel blocks used by a naive bilinear or bicubic interpolation method. As the shrink factor grows larger, so should the pixel block used by the filter, otherwise you get aliasing artifacts as you've seen here.

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