給定您的輸入圖像，注釋中第一個鏈接的答案中的方法(對Chris Campbell表示敬意)將產生以下縮略圖之一：

(另一個是您使用MS Paint創建的縮略圖。很難稱其中一個比另一個“更好” ...)

編輯：只是要指出這一點：原始代碼的主要問題是您并沒有真正按比例縮放圖像。 您只是使用了一個奇怪的循環來“計算”目標大小。 關鍵是您實際上要分多個步驟執行縮放。

為了完整起見，MVCE

(編輯：我提到了Chris Campbell，并通過注釋引用了源代碼，但在此要更清楚：以下內容基于《 Perils of Image.getScaledInstance()》)

import java.awt.Graphics2D;

import java.awt.RenderingHints;

import java.awt.Transparency;

import java.awt.image.BufferedImage;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.OutputStream;

import java.util.Iterator;

import javax.imageio.IIOImage;

import javax.imageio.ImageIO;

import javax.imageio.ImageWriteParam;

import javax.imageio.ImageWriter;

import javax.imageio.stream.ImageOutputStream;

import javax.imageio.stream.MemoryCacheImageOutputStream;

public class ResizeQuality

{

public static void main(String[] args) throws IOException

{

BufferedImage image = ImageIO.read(new File("X0aPT.jpg"));

BufferedImage scaled = getScaledInstance(

image, 51, 75, RenderingHints.VALUE_INTERPOLATION_BILINEAR, true);

writeJPG(scaled, new FileOutputStream("X0aPT_tn.jpg"), 0.85f);

}

public static BufferedImage getScaledInstance(

BufferedImage img, int targetWidth,

int targetHeight, Object hint,

boolean higherQuality)

{

int type =

(img.getTransparency() == Transparency.OPAQUE)

? BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;

BufferedImage ret = (BufferedImage) img;

int w, h;

if (higherQuality)

{

// Use multi-step technique: start with original size, then

// scale down in multiple passes with drawImage()

// until the target size is reached

w = img.getWidth();

h = img.getHeight();

}

else

{

// Use one-step technique: scale directly from original

// size to target size with a single drawImage() call

w = targetWidth;

h = targetHeight;

}

do

{

if (higherQuality && w > targetWidth)

{

w /= 2;

if (w < targetWidth)

{

w = targetWidth;

}

}

if (higherQuality && h > targetHeight)

{

h /= 2;

if (h < targetHeight)

{

h = targetHeight;

}

}

BufferedImage tmp = new BufferedImage(w, h, type);

Graphics2D g2 = tmp.createGraphics();

g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, hint);

g2.drawImage(ret, 0, 0, w, h, null);

g2.dispose();

ret = tmp;

} while (w != targetWidth || h != targetHeight);

return ret;

}

public static void writeJPG(

BufferedImage bufferedImage,

OutputStream outputStream,

float quality) throws IOException

{

Iterator iterator =

ImageIO.getImageWritersByFormatName("jpg");

ImageWriter imageWriter = iterator.next();

ImageWriteParam imageWriteParam = imageWriter.getDefaultWriteParam();

imageWriteParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);

imageWriteParam.setCompressionQuality(quality);

ImageOutputStream imageOutputStream =

new MemoryCacheImageOutputStream(outputStream);

imageWriter.setOutput(imageOutputStream);

IIOImage iioimage = new IIOImage(bufferedImage, null, null);

imageWriter.write(null, iioimage, imageWriteParam);

imageOutputStream.flush();

}

}

總結

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