这篇文章上次修改于 2005 天前，可能其部分内容已经发生变化，如有疑问可询问作者。 >参考帖子https://stackoverflow.com/questions/7951290/re-sizing-an-image-without-losing-quality/16859589 1.代码如下 ```java package com.tddlmj.rstar.util; import javax.imageio.ImageIO; import java.awt.*; import java.awt.image.BufferedImage; import java.io.File; import java.io.IOException; import static java.awt.RenderingHints.VALUE_INTERPOLATION_BICUBIC; /** * 封面是674/1000 * s---103 * b----182 */ public class ImgUtil { public static void convertToWidth(float width, String path) { } /** * Resizes an image to a absolute width and height (the image may not be * proportional) * * @param inputImagePath Path of the original image * @param outputImagePath Path to save the resized image * @param scaledWidth absolute width in pixels * @param scaledHeight absolute height in pixels * @throws IOException */ public static void resize(String inputImagePath, String outputImagePath, int scaledWidth, int scaledHeight) throws IOException { // reads input image File inputFile = new File(inputImagePath); BufferedImage inputImage = ImageIO.read(inputFile); // creates output image // BufferedImage outputImage = new BufferedImage(scaledWidth, // scaledHeight, inputImage.getType()); BufferedImage outputImage = getScaledInstance(inputImage,scaledWidth,scaledHeight, VALUE_INTERPOLATION_BICUBIC,true); // scales the input image to the output image Graphics2D g2d = outputImage.createGraphics(); g2d.drawImage(inputImage, 0, 0, scaledWidth, scaledHeight, null); g2d.dispose(); // extracts extension of output file String formatName = outputImagePath.substring(outputImagePath .lastIndexOf(".") + 1); // writes to output file ImageIO.write(outputImage, formatName, new File(outputImagePath)); } /** * Resizes an image by a percentage of original size (proportional). * * @param inputImagePath Path of the original image * @param outputImagePath Path to save the resized image * @param percent a double number specifies percentage of the output image * over the input image. * @throws IOException */ public static void resize(String inputImagePath, String outputImagePath, double percent) throws IOException { File inputFile = new File(inputImagePath); BufferedImage inputImage = ImageIO.read(inputFile); int scaledWidth = (int) (inputImage.getWidth() * percent); int scaledHeight = (int) (inputImage.getHeight() * percent); resize(inputImagePath, outputImagePath, scaledWidth, scaledHeight); } /** * Resizes an image by a percentage of original size (proportional). * * @param inputImagePath Path of the original image * @param outputImagePath Path to save the resized image * @param width a fixed width * over the input image. * @throws IOException */ public static void resizeFixWidth(String inputImagePath, String outputImagePath, int width) throws IOException { File inputFile = new File(inputImagePath); BufferedImage inputImage = ImageIO.read(inputFile); int scaledWidth = width; float percent = (float)width /inputImage.getWidth(); int scaledHeight = (int) (inputImage.getHeight() * percent); resize(inputImagePath, outputImagePath, scaledWidth, scaledHeight); } //https://stackoverflow.com/questions/7951290/re-sizing-an-image-without-losing-quality/16859589 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; } /** * Test resizing images */ public static void main(String[] args) { String inputImagePath = "/home/shenfeng/Downloads/3434s.jpg"; String outputImagePath1 = "D:/Photo/Puppy_Fixed.jpg"; String outputImagePath2 = "/home/shenfeng/Downloads/333.jpg"; String outputImagePath3 = "D:/Photo/Puppy_Bigger.jpg"; try { // resize to a fixed width (not proportional) // int scaledWidth = 1024; // int scaledHeight = 768; // ImgUtil.resize(inputImagePath, outputImagePath1, scaledWidth, scaledHeight); // resize smaller by 50% ImgUtil.resizeFixWidth(inputImagePath, outputImagePath2, 103); // resize bigger by 50% // percent = 1.5; // ImgUtil.resize(inputImagePath, outputImagePath3, percent); } catch (IOException ex) { System.out.println("Error resizing the image."); ex.printStackTrace(); } } } ``` 2.传值解释如下： ```bash VALUE_INTERPOLATION_NEAREST_NEIGHBOR: Specific hint that provides higher performance, but lower-quality, "blocky" results. VALUE_INTERPOLATION_BILINEAR: Specific hint that is typically a bit slower, but provides higher-quality, "filtered" results. VALUE_INTERPOLATION_BICUBIC: Specific hint that is similar to BILINEAR except that it uses more samples when filtering and therefore has generally higher quality than BILINEAR. (Note: this hint constant has been available since JDK 1.2, but was not implemented by Sun until the JDK 5 release; prior to that release, this hint was synonymous with BILINEAR.) ```
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