参考帖子https://stackoverflow.com/questions/7951290/re-sizing-an-image-without-losing-quality/16859589
1.代码如下
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：
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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