java图片处理

缩放图片的代码

public 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;
    }

 

将InputStream保存为jpg文件 

public static void saveImageAsJpg (InputStream in, File saveFile,int width,int hight)    
            throws Exception {
        BufferedImage srcImage;

        srcImage = ImageIO.read(in);

        if(width > 0 || hight > 0)
        {
             srcImage = resize(srcImage, width, hight);
        }

        ImageIO.write(srcImage, "JPEG", saveFile);
        in.close();
    }

将InputStream保存为gif文件

private static void saveImageAsGif(InputStream in, File fileToSave,int width, int hight)
            throws Exception {
        BufferedImage srcImage;

        srcImage = ImageIO.read(in);

        if(width>0 && hight >0)
        {
             srcImage = resize(srcImage, width, hight);
        }

        FileOutputStream out = new FileOutputStream(fileToSave);
        GifEncoder encoder = new GifEncoder(srcImage, out);
        encoder.encode();

        in.close();
    }