Image Resolution Changing but I am only trying to rotate the image

Question

Any reason this code would changing the resolution of the original JPEG? I can understand if the file size were different because the JPEG quality settings are probably different but I don't understand why this would be resizing an image.

File newfile=new File(mydestinationfolder.concat(imagename));
Files.move(file.toPath(),newfile.toPath(), REPLACE_EXISTING);
Rotation Orientation;
if ((Orientation=Exif_data.get_Exif_Orientation(newfile)) != null) {

    System.out.println(Orientation.toString());
    BufferedImage oldimage = ImageIO.read(newfile);
    BufferedImage tmp = Scalr.rotate(oldimage, Orientation);
    oldimage.flush();
    oldimage=tmp;
    ImageIO.write(oldimage, "JPEG", newfile);

}

Answer 1

Well I am not sure why but the default settings for ImageIO.write() are changing the resolution. If I define a custom writer with JPEG quality set to 100%, the image resolution stays the same.

NOTE: output.close() at the end is important because as long as the stream is open the file is locked.

BufferedImage oldimage = ImageIO.read(newfile);
BufferedImage tmp = Scalr.rotate(oldimage, Orientation);
oldimage.flush();
oldimage=tmp;
Iterator iter = ImageIO.getImageWritersByFormatName("jpeg");
ImageWriter writer = (ImageWriter)iter.next();
ImageWriteParam iwp = writer.getDefaultWriteParam();
iwp.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
float quality=1.0f;
iwp.setCompressionQuality(quality);

FileImageOutputStream output = new FileImageOutputStream(newfile);
writer.setOutput(output);

IIOImage image = new IIOImage(oldimage, null, null);
writer.write(null, image, iwp);
writer.dispose();
output.close();

Answer 2

Late answer, but anyway..

As a JPEG read/manipulate/write cycle using ImageIO is always going to be lossy, and all you are doing is rotating, you should have a look at LLJTran from mediautil, as mentioned in this thread.

With that package, you should be able to benefit from a special feature of JPEG block compression to do a lossless JPEG transformation.

Still don't understand why your original code would change the image resolution, nor why your proposed solution would fix it though... Sounds like a bug to me, and should be reported to Oracle. What I do know though, is that setting the JPEG quality to 1.0 (100%) isn't what JPEG was meant for, and is going to cause huge files with no gain in quality (it may possibly be worse than storing at the quality of the original) given the input is already a compressed JPEG .