Saving colorspace in jpeg

问题

I have a servlet to convert and cache smaller versions of photographs. It is implemented using java.awt.image + javax.imageio and a third party resample filter. The originals are all uploaded with an sRGB color profile. When I resample them and save them again they still are in sRGB however this is not recorded in the saved file.

How can I make sure this information is saved in the file?

In case you wondered it makes a difference, images without a profile are much more saturated on my screen (Safari + OSX + Calibrated screen) then when they have the correct sRGB profile. Also I'm sure it's the missing profile information and not the resampling algorithm.

回答1:

Turns out it is enough to include an EXIF tag ColorSpace=1 that tells it should be processed as sRGB. Succeeded into doing this using Apache Commons Sanselan. This library is unfortunatly not complete so it can only be used to modify the EXIF after the file has been created.

Relevant code, based on Sanselan example:

public void addExifMetadata(File jpegImageFile, File dst)
            throws IOException, ImageReadException, ImageWriteException {
        OutputStream os = null;
        try {
            TiffOutputSet outputSet = new TiffOutputSet();

            TiffOutputField colorspace = TiffOutputField.create(
                        TiffConstants.EXIF_TAG_COLOR_SPACE, outputSet.byteOrder, new Integer(1));
            TiffOutputDirectory exifDirectory = outputSet.getOrCreateExifDirectory();
            exifDirectory.add(colorspace);

            os = new FileOutputStream(dst);
            os = new BufferedOutputStream(os);
            new ExifRewriter().updateExifMetadataLossless(jpegImageFile, os, outputSet);

            os.close();
            os = null;
        } finally  {
            if (os != null)
                try {
                    os.close();
                } catch (IOException e) {

                }
        }
    }

来源：https://stackoverflow.com/questions/5586671/saving-colorspace-in-jpeg