first I'd like to explain the situation/requirements that lead to the question:
In our web application we can't support CMYK images (JPEG) since IE 8 and below can't display them.
Thus we need to detect when someone wants to upload such an image and deny it.
Unfortunately, Java's ImageIO won't read those images or would not enable me to get the detected color space. From debugging it seems like JPEGImageReader internally gets the color space code 11 (which would mean JCS_YCCK) but I can't safely access that information.
When querying the reader for the image types I get nothing for CMYK, so I might assume no image types = unsupported image.
I converted the source CMYK image to RGB using an imaging tool in order to test whether it would then be readable (I tried to simulate the admin's steps when getting the message "No CMYK supported"). However, JPEGImageReader would not read that image, since it assumes (comment in the source!)3-component RGB color space but the image header reports 4 components (maybe RGBA or ARGB) and thus an IllegalArgumentException is thrown.
Thus, ImageIO is not an option since I can't reliably get the color space of an image and I can't tell the admin why an otherwise fine image (it can be displayed by the browser) would not be accepted due to some internal error.
This led me to try JAI ImageIO whose CLibJPEGImageReader does an excellent job and correctly reads all my test images.
However, since we're deploying our application in a JBoss that might host other applications as well, we'd like to keep them as isolated as possible. AFAIK, I'd need to install JAI ImageIO to the JRE or otherwise make the native libs available in order to use them, and thus other applications might get access to them as well, which might cause side effects (at least we'd have to test a lot to ensure that's not the case).
That's the explanation for the question, and here it comes again:
Is there any pure Java alternative to JAI ImageIO which reliably detects and possibly converts CMYK images?
Thanks in advance,
Thomas
I found a solution that is ok for our needs: Apache Commons Sanselan. This library reads JPEG headers quite fast and accurate (at least all my test images) as well as a number of other image formats.
The downside is that it won't read JPEG image data, but I can do that with the basic JRE tools.
Reading JPEG images for conversion is quite easy (the ones that ImageIO refuses to read, too):
JPEGImageDecoder decoder = JPEGCodec.createJPEGDecoder(new FileInputStream( new File(pFilename) ) );
BufferedImage sourceImg = decoder.decodeAsBufferedImage();
Then if Sanselan tells me the image is actually CMYK, I get the source image's raster and convert myself:
for( /*each pixel in the raster, which is represented as int[4]*/ )
{
double k = pixel[3] / 255.0;
double r = (255.0 - pixel[0])*k;
double g = (255.0 - pixel[1])*k;
double b = (255.0 - pixel[2])*k;
}
This give quite good results in the RGB images not being too bright or dark. However, I'm not sure why multiplying with k prevents the brightening. The JPEG is actually decoded in native code and the CMYK->RGB conversion I got states something different, I just tried the multiply to see the visual result.
If anybody could shed some light on this, I'd be grateful.
I've posted a pure Java solution for reading all sorts of JPEG images and converting them to RGB.
It's built on the following facts:
- While ImageIO cannot read JPEG images with CMYK as a buffered image, it can read the raw pixel data (raster).
- Sanselan (or Apache Commons Imaging as it's called now) can be used to read the details of CMYK images.
- There are images with inverted CMYK values (an old Photoshop bug).
- There are images with YCCK instead of CMYK (can easily be converted).
In our web application we can't support CMYK images (JPEG) since
IE 8 and below can't display them. Thus we need to detect when someone
wants to upload such an image and deny it.
I don't agree with your "Thus we need to detect when someone wants to upload such an image and deny it". A much more user-friendly policy would be to convert it to something else than CMYK.
The rest of your post is a bit confusing in that regards seen that you ask both for detection and conversion, which are two different things. Once again, I think converting the image is much more user-friendly.
No need to write in bold btw:
Is there any pure Java alternative to JAI ImageIO which reliably
detects and possibly converts CMYK images?
Pure Java I don't know, but ImageMagick works fine to convert CMYK image to RGB ones. Calling ImageMagick on the server-side from Java really isn't complicated. I used to do it manually by calling an external process but nowadays there are wrappers like JMagick and im4java.
Beware of another post as the Java 7 does not allow to use directly Sun's implementation without special parameters as indicated in import com.sun.image.codec.jpeg.*.
