Java上传pdf文件，只压缩大小，不改变成.zip/.rar文件

可以，压缩只是一种算法，什么语言都可以，比如某种格式的文件中1001010(二进制)代表汉子的"中"字，那么压缩算法就是在编码不冲突的情况下可以改变编码长度，比如压缩之后中字变成1010，这样就节省空间了，这是我随便举的例子，具体的对应算法可以网上查

 可以使用Draw这个类，通过改变像素来改变存储大小，实例如下：

public static boolean compressPic(String srcFilePath, String descFilePath) throws IOException {

        File file = null

        BufferedImage src = null

        FileOutputStream out = null

        ImageWriter imgWrier

        ImageWriteParam imgWriteParams

        // 指定写图片的方式为 jpg

        imgWrier = ImageIO.getImageWritersByFormatName("jpg").next()

        imgWriteParams = new javax.imageio.plugins.jpeg.JPEGImageWriteParam(

                null)

        // 要使用压缩，必须指定压缩方式为MODE_EXPLICIT

        imgWriteParams.setCompressionMode(imgWriteParams.MODE_EXPLICIT)

        // 这里指定压缩的程度，参数qality是取值0~1范围内，

        imgWriteParams.setCompressionQuality((float) 1)

        imgWriteParams.setProgressiveMode(imgWriteParams.MODE_DISABLED)

        ColorModel colorModel =ImageIO.read(new File(srcFilePath)).getColorModel()// ColorModel.getRGBdefault()

        // 指定压缩时使用的色彩模式

//        imgWriteParams.setDestinationType(new javax.imageio.ImageTypeSpecifier(

//                colorModel, colorModel.createCompatibleSampleModel(16, 16)))

        imgWriteParams.setDestinationType(new javax.imageio.ImageTypeSpecifier(

                colorModel, colorModel.createCompatibleSampleModel(16, 16)))

        try {

            if (isBlank(srcFilePath)) {

                return false

            } else {

                file = new File(srcFilePath)System.out.println(file.length())

                src = ImageIO.read(file)

                out = new FileOutputStream(descFilePath)

                imgWrier.reset()

                // 必须先指定 out值，才能调用write方法, ImageOutputStream可以通过任何

                // OutputStream构造

                imgWrier.setOutput(ImageIO.createImageOutputStream(out))

                // 调用write方法，就可以向输入流写图片

                imgWrier.write(null, new IIOImage(src, null, null),

                        imgWriteParams)

                out.flush()

                out.close()

            }

        } catch (Exception e) {

            e.printStackTrace()

            return false

        }

        return true

    }

public static boolean isBlank(String string) {

        if (string == null || string.length() == 0 || string.trim().equals("")) {

            return true

        }

        return false

    }

//将图按比例缩小。

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_RENDERING, RenderingHints.VALUE_RENDER_QUALITY )

g.drawRenderedImage(source, AffineTransform.getScaleInstance(sx, sy))

g.dispose()

return target

}

public static void saveImageAsJpg (String fromFileStr,String saveToFileStr,int width,int hight)

throws Exception {

BufferedImage srcImage

// String ex = fromFileStr.substring(fromFileStr.indexOf("."),fromFileStr.length())

String imgType = "JPEG"

if (fromFileStr.toLowerCase().endsWith(".png")) {

imgType = "PNG"

}

// System.out.println(ex)

File saveFile=new File(saveToFileStr)

File fromFile=new File(fromFileStr)

srcImage = ImageIO.read(fromFile)

if(width >0 || hight >0)

{

srcImage = resize(srcImage, width, hight)

}

ImageIO.write(srcImage, imgType, saveFile)

}

public static void main (String argv[]) {

try{

//参数1(from),参数2(to),参数3(宽),参数4(高)

saveImageAsJpg("C:\\Documents and Settings\\xugang\\桌面\\tmr-06.jpg",

"C:\\Documents and Settings\\xugang\\桌面\\2.jpg",

120,120)

} catch(Exception e){

e.printStackTrace()

}

}

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