问题描述：大小在100M~2G，格式为tiff、tif的图片，需要转成web能够预览的格式为JPG或PNG，大小在500kb左右的图片
ImageIO类和Java Advanced Imaging Api可行，给你一个官方的案例：
File inputFile = new File("originalImage.tif");
BufferedImage inputImage = ImageIO.read(inputFile);
int newWidth = 800;
int newHeight = 600;
BufferedImage scaledImage = new BufferedImage(newWidth, newHeight, inputImage.getType());
Graphics2D graphics2D = scaledImage.createGraphics();
graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
graphics2D.drawImage(inputImage, 0, 0, newWidth, newHeight, null);
graphics2D.dispose();
File outputFile = new File("scaledImage.jpg");
ImageIO.write(scaledImage, "jpg", outputFile);
/**
*
* 功能描述: 图片转tif格式
*
* @param: [fileAbsolutePath]
* @return: java.lang.String 转成TIF图片的地址全路径
* @auther: KevinZc
* @date: 2018/9/8 22:14
*/
public String image2Tif(String fileAbsolutePath){
OutputStream outputStream = null;
String filterFilePath = null;
String tifFilePath = null;
ImageOutputStream ios = null;
try {
// 解决位深度太小 start ====注意：8位深度的图片会出现文件损坏问题
File picture = new File(fileAbsolutePath);
// 统一进行一次过滤 转换成24位深度
filterFilePath = fileAbsolutePath.substring(0, fileAbsolutePath.lastIndexOf("."))+".JPG";
tifFilePath = filterFilePath.substring(0, filterFilePath.lastIndexOf("."))+".tif";
ios = ImageIO.createImageOutputStream(new File(filterFilePath));
ImageIO.write(ImageIO.read(picture),"JPG", ios);
// 解决位深度太小 end
FileSeekableStream stream = new FileSeekableStream(filterFilePath);
PlanarImage in = JAI.create("stream", stream);
OutputStream os = null;
os = new FileOutputStream(tifFilePath);
// 设置dpi为300
TIFFEncodeParam param = new TIFFEncodeParam();
param.setCompression(TIFFEncodeParam.COMPRESSION_NONE);
TIFFField[] extras = new TIFFField[2];
extras[0] = new TIFFField(282, TIFFTag.TIFF_RATIONAL, 1, (Object) new long[][]{{(long) 300, 1}, {0, 0}});
// extras[0] = new TIFFField(282, TIFFTag.TIFF_RATIONAL, 1, (Object) new long[][]{{(long) dpi, 1}, {0, 0}});
extras[1] = new TIFFField(283, TIFFTag.TIFF_RATIONAL, 1, (Object) new long[][]{{(long) 300, 1}, {0, 0}});
param.setExtraFields(extras);
TIFFImageEncoder enc = new TIFFImageEncoder(os, param);
try {
enc.encode(in);
os.flush();
os.close();
stream.close();
} catch (Exception e) {
logger.error("{}",e );
throw new RuntimeException(e);
}
return tifFilePath;
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (outputStream != null) {
outputStream.close();
}
if (ios != null) {
ios.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
对于这个问题，可以使用Java的开源库ImageIO来实现TIF格式图像转码和缩略处理，并控制大小在500KB左右。
以下是具体步骤：
File tifFile = new File("path/to/tif/file.tif");
ImageInputStream input = ImageIO.createImageInputStream(tifFile);
Iterator<ImageReader> readers = ImageIO.getImageReaders(input);
ImageReader reader = readers.next();
reader.setInput(input);
BufferedImage tifImage = reader.read(0);//读取第一帧，多帧需要循环读取
//根据需要转换成JPG或PNG格式
BufferedImage outImage = new BufferedImage(image.getWidth(), image.getHeight(), BufferedImage.TYPE_INT_RGB);
outImage.createGraphics().drawImage(image, 0, 0, Color.WHITE, null);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ImageIO.write(outImage, "jpg", baos);
//压缩图片大小，控制在500KB以内
long length = baos.toByteArray().length;
double rate = Math.sqrt(500000d / length);
if(rate > 1) {
//如果小于500KB，则直接输出
ImageIO.write(outImage, "jpg", response.getOutputStream());
} else {
//如果大于500KB，则缩小图片，再输出
BufferedImage newImage = Thumbnails.of(outImage).scale(rate).asBufferedImage();
ImageIO.write(newImage, "jpg", response.getOutputStream());
}
需要注意的问题：
使用Image Optimizer