java 实现对图片进行指定的缩小或放大
import java.awt.Graphics2D; import java.awt.Rectangle; import java.awt.RenderingHints; import java.awt.geom.AffineTransform; import java.awt.image.BufferedImage; import java.awt.image.ColorModel; import java.awt.image.WritableRaster; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import javax.imageio.ImageIO; /** * 图片工具类，完成图片的截取 * * @author inc062977 * */ public class AlterUploadImage { /** * 实现图像的等比缩放 * @param source * @param targetW * @param targetH * @return */ private static BufferedImage resize(BufferedImage source, int targetW, int targetH) { // targetW，targetH分别表示目标长和宽 int type = source.getType(); BufferedImage target = null; double sx = (double) targetW / source.getWidth(); double sy = (double) targetH / source.getHeight(); // 这里想实现在targetW，targetH范围内实现等比缩放。如果不需要等比缩放 // 则将下面的if else语句注释即可 if (sx < sy) { sx = sy; targetW = (int) (sx * source.getWidth()); } else { sy = sx; targetH = (int) (sy * source.getHeight()); } if (type == BufferedImage.TYPE_CUSTOM) { // handmade ColorModel cm = source.getColorModel(); WritableRaster raster = cm.createCompatibleWritableRaster(targetW, targetH); boolean alphaPremultiplied = cm.isAlphaPremultiplied(); target = new BufferedImage(cm, raster, alphaPremultiplied, null); } else target = new BufferedImage(targetW, targetH, type); Graphics2D g = target.createGraphics(); // smoother than exlax: g.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC); g.drawRenderedImage(source, AffineTransform.getScaleInstance(sx, sy)); g.dispose(); return target; } /** * 实现图像的等比缩放和缩放后的截取 * @param inFilePath 要截取文件的路径 * @param outFilePath 截取后输出的路径 * @param width 要截取宽度 * @param hight 要截取的高度 * @param proportion * @throws Exception */ public static void saveImageAsJpg(String inFilePath, String outFilePath, int width, int hight, boolean proportion)throws Exception { File file = new File(inFilePath); InputStream in = new FileInputStream(file); File saveFile = new File(outFilePath); BufferedImage srcImage = ImageIO.read(in); if (width > 0 || hight > 0) { // 原图的大小 int sw = srcImage.getWidth(); int sh = srcImage.getHeight(); // 如果原图像的大小小于要缩放的图像大小，直接将要缩放的图像复制过去 if (sw > width && sh > hight) { srcImage = resize(srcImage, width, hight); } else { String fileName = saveFile.getName(); String formatName = fileName.substring(fileName .lastIndexOf('.') + 1); ImageIO.write(srcImage, formatName, saveFile); return; } } // 缩放后的图像的宽和高 int w = srcImage.getWidth(); int h = srcImage.getHeight(); // 如果缩放后的图像和要求的图像宽度一样，就对缩放的图像的高度进行截取 if (w == width) { // 计算X轴坐标 int x = 0; int y = h / 2 - hight / 2; saveSubImage(srcImage, new Rectangle(x, y, width, hight), saveFile); } // 否则如果是缩放后的图像的高度和要求的图像高度一样，就对缩放后的图像的宽度进行截取 else if (h == hight) { // 计算X轴坐标 int x = w / 2 - width / 2; int y = 0; saveSubImage(srcImage, new Rectangle(x, y, width, hight), saveFile); } in.close(); } /** * 实现缩放后的截图 * @param image 缩放后的图像 * @param subImageBounds 要截取的子图的范围 * @param subImageFile 要保存的文件 * @throws IOException */ private static void saveSubImage(BufferedImage image, Rectangle subImageBounds, File subImageFile) throws IOException { if (subImageBounds.x < 0 || subImageBounds.y < 0 || subImageBounds.width - subImageBounds.x > image.getWidth() || subImageBounds.height - subImageBounds.y > image.getHeight()) { System.out.println("Bad subimage bounds"); return; } BufferedImage subImage = image.getSubimage(subImageBounds.x,subImageBounds.y, subImageBounds.width, subImageBounds.height); String fileName = subImageFile.getName(); String formatName = fileName.substring(fileName.lastIndexOf('.') + 1); ImageIO.write(subImage, formatName, subImageFile); } public static void main(String[] args) { AlterUploadImage au = new AlterUploadImage(); try { au.saveImageAsJpg("d://psu[3].jpg", "d://new.jpg", 900, 800, true); System.out.println("Done"); } catch (Exception e) { e.printStackTrace(); } }}
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