一個JAVA圖形縮放處理工具類

調用的例子

import java.io.FileOutputStream;

import java.io.IOException;

import javax.imageio.ImageIO;

public class T {

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

ImageIO.write(ImageUtils.resizeImage("d:/www.java2000.net.gif", ImageUtils.IMAGE_GIF, 30, 20),

"JPEG", new FileOutputStream("d:/test.jpg"));

}

}

import java.awt.Dimension;

import java.awt.Image;

import java.awt.image.BufferedImage;

import java.awt.image.PixelGrabber;

import java.io.File;

import java.io.IOException;

import java.util.Iterator;

import java.util.Locale;

import javax.imageio.IIOImage;

import javax.imageio.ImageIO;

import javax.imageio.ImageWriteParam;

import javax.imageio.ImageWriter;

import javax.imageio.plugins.jpeg.JPEGImageWriteParam;

import javax.imageio.stream.ImageOutputStream;

public class ImageUtils {

public static final int IMAGE_UNKNOWN = -1;

public static final int IMAGE_JPEG = 0;

public static final int IMAGE_PNG = 1;

public static final int IMAGE_GIF = 2;

/**

* Resizes an image

*

* @param imgName

* The image name to resize. Must be the complet path to the file

* @param type

* int

* @param maxWidth

* The image's max width

* @param maxHeight

* The image's max height

* @return A resized BufferedImage

*/

public static BufferedImage resizeImage(String imgName, int type, int maxWidth, int maxHeight) {

try {

return resizeImage(ImageIO.read(new File(imgName)), type, maxWidth, maxHeight);

} catch (IOException e) {

e.printStackTrace();

return null;

}

}

/**

* Resizes an image.

*

* @param image

* The image to resize

* @param maxWidth

* The image's max width

* @param maxHeight

* The image's max height

* @return A resized BufferedImage

* @param type

* int

*/

public static BufferedImage resizeImage(BufferedImage image, int type, int maxWidth, int maxHeight) {

Dimension largestDimension = new Dimension(maxWidth, maxHeight);

// Original size

int imageWidth = image.getWidth(null);

int imageHeight = image.getHeight(null);

float aspectRatio = (float) imageWidth / imageHeight;

if (imageWidth > maxWidth || imageHeight > maxHeight) {

if ((float) largestDimension.width / largestDimension.height > aspectRatio) {

largestDimension.width = (int) Math.ceil(largestDimension.height * aspectRatio);

} else {

largestDimension.height = (int) Math.ceil(largestDimension.width / aspectRatio);

}

imageWidth = largestDimension.width;

imageHeight = largestDimension.height;

}

return createHeadlessSmoothBufferedImage(image, type, imageWidth, imageHeight);

}

/**

* Saves an image to the disk.

*

* @param image

* The image to save

* @param toFileName

* The filename to use

* @param type

* The image type. Use ImageUtils.IMAGE_JPEG to save as

* JPEG images, or ImageUtils.IMAGE_PNG to save as PNG.

* @return false if no appropriate writer is found

*/

public static boolean saveImage(BufferedImage image, String toFileName, int type) {

try {

return ImageIO.write(image, type == IMAGE_JPEG ? "jpg" : "png", new File(toFileName));

} catch (IOException e) {

e.printStackTrace();

return false;

}

}

/**

* Compress and save an image to the disk. Currently this method only supports

* JPEG images.

*

* @param image

* The image to save

* @param toFileName

* The filename to use

* @param type

* The image type. Use ImageUtils.IMAGE_JPEG to save as

* JPEG images, or ImageUtils.IMAGE_PNG to save as PNG.

*/

public static void saveCompressedImage(BufferedImage image, String toFileName, int type) {

try {

if (type == IMAGE_PNG) {

throw new UnsupportedOperationException("PNG compression not implemented");

}

Iterator iter = ImageIO.getImageWritersByFormatName("jpg");

ImageWriter writer;

writer = (ImageWriter) iter.next();

ImageOutputStream ios = ImageIO.createImageOutputStream(new File(toFileName));

writer.setOutput(ios);

ImageWriteParam iwparam = new JPEGImageWriteParam(Locale.getDefault());

iwparam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);

iwparam.setCompressionQuality(0.7F);

writer.write(null, new IIOImage(image, null, null), iwparam);

ios.flush();

writer.dispose();

ios.close();

} catch (IOException e) {

e.printStackTrace();

}

}

/**

* Creates a BufferedImage from an Image. This

* method can function on a completely headless system. This especially

* includes Linux and Unix systems that do not have the X11 libraries

* installed, which are required for the AWT subsystem to operate. This method

* uses nearest neighbor approximation, so it's quite fast. Unfortunately, the

* result is nowhere near as nice looking as the

* createHeadlessSmoothBufferedImage method.

*

* @param image

* The image to convert

* @param w

* The desired image width

* @param h

* The desired image height

* @return The converted image

* @param type

* int

*/

public static BufferedImage createHeadlessBufferedImage(BufferedImage image, int type, int width,

int height) {

if (type == ImageUtils.IMAGE_PNG && hasAlpha(image)) {

type = BufferedImage.TYPE_INT_ARGB;

} else {

type = BufferedImage.TYPE_INT_RGB;

}

BufferedImage bi = new BufferedImage(width, height, type);

for (int y = 0; y < height; y++) {

for (int x = 0; x < width; x++) {

bi.setRGB(x, y, image.getRGB(x * image.getWidth() / width, y * image.getHeight() / height));

}

}

return bi;

}

/**

* Creates a BufferedImage from an Image. This

* method can function on a completely headless system. This especially

* includes Linux and Unix systems that do not have the X11 libraries

* installed, which are required for the AWT subsystem to operate. The

* resulting image will be smoothly scaled using bilinear filtering.

*

* @param source

* The image to convert

* @param w

* The desired image width

* @param h

* The desired image height

* @return The converted image

* @param type

* int

*/

public static BufferedImage createHeadlessSmoothBufferedImage(BufferedImage source, int type,

int width, int height) {

if (type == ImageUtils.IMAGE_PNG && hasAlpha(source)) {

type = BufferedImage.TYPE_INT_ARGB;

} else {

type = BufferedImage.TYPE_INT_RGB;

}

BufferedImage dest = new BufferedImage(width, height, type);

int sourcex;

int sourcey;

double scalex = (double) width / source.getWidth();

double scaley = (double) height / source.getHeight();

int x1;

int y1;

double xdiff;

double ydiff;

int rgb;

int rgb1;

int rgb2;

for (int y = 0; y < height; y++) {

sourcey = y * source.getHeight() / dest.getHeight();

ydiff = scale(y, scaley) - sourcey;

for (int x = 0; x < width; x++) {

sourcex = x * source.getWidth() / dest.getWidth();

xdiff = scale(x, scalex) - sourcex;

x1 = Math.min(source.getWidth() - 1, sourcex + 1);

y1 = Math.min(source.getHeight() - 1, sourcey + 1);

rgb1 = getRGBInterpolation(source.getRGB(sourcex, sourcey), source.getRGB(x1, sourcey),

xdiff);

rgb2 = getRGBInterpolation(source.getRGB(sourcex, y1), source.getRGB(x1, y1), xdiff);

rgb = getRGBInterpolation(rgb1, rgb2, ydiff);

dest.setRGB(x, y, rgb);

}

}

return dest;

}

private static double scale(int point, double scale) {

return point / scale;

}

private static int getRGBInterpolation(int value1, int value2, double distance) {

int alpha1 = (value1 & 0xFF000000) >>> 24;

int red1 = (value1 & 0x00FF0000) >> 16;

int green1 = (value1 & 0x0000FF00) >> 8;

int blue1 = (value1 & 0x000000FF);

int alpha2 = (value2 & 0xFF000000) >>> 24;

int red2 = (value2 & 0x00FF0000) >> 16;

int green2 = (value2 & 0x0000FF00) >> 8;

int blue2 = (value2 & 0x000000FF);

int rgb = ((int) (alpha1 * (1.0 - distance) + alpha2 * distance) << 24)

| ((int) (red1 * (1.0 - distance) + red2 * distance) << 16)

| ((int) (green1 * (1.0 - distance) + green2 * distance) << 8)

| (int) (blue1 * (1.0 - distance) + blue2 * distance);

return rgb;

}

/**

* Determines if the image has transparent pixels.

*

* @param image

* The image to check for transparent pixel.s

* @return true of false, according to the result

*/

public static boolean hasAlpha(Image image) {

try {

PixelGrabber pg = new PixelGrabber(image, 0, 0, 1, 1, false);

pg.grabPixels();

return pg.getColorModel().hasAlpha();

} catch (InterruptedException e) {

return false;

}

}

}

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