Image Processing - Jpeg

Nidge_Weasel

Ok guys, working on my final year project here, and need some help, need to be able to take a BMP image, transform those into YCbCr values, perform a DCT on them, quantize them and then write this as a JPEG. writing the Jpeg is the problem, can get as far as the quantization stage, and now i need help, does anyone know if there is a Java library out there to do huffman coding that is Jpeg compliant, or does anyone know, do i even really need to perform the encoding in order for it to be a jpeg usable by any graphics software? Please help!! thanks!!

CreepingDeath

Nidge_Weasel wrote: »

writing the Jpeg is the problem

There's standard Java libraries which perform this.
You don't need to worry about how it's implemented.

You can control the compression versus image quality with a parameter from 0 - 1 ( floating point number ).
0 = best compression ( lossy compression = worst image quality )
1 = lossless compression ( best quality, larger file sizes )
0.8 = compromise between losing some quality for smaller file sizes


Here's some code from a utility class of mine to store JPEGs and PNGs.
I've thrown in some of the imports, might have missed some though..

// Imports
import java.awt.image.BufferedImage;
import java.awt.image.RenderedImage;
import java.awt.image.renderable.ParameterBlock;
import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageWriteParam;
import javax.imageio.ImageWriter;
import javax.imageio.stream.FileImageOutputStream;


     public static boolean savePNG(final String filename, final Image photo, final float quality)
    {
        return (saveImage(filename, "png", photo, quality));
    }

    
    public static boolean saveJPEG(final String filename, final Image photo, final float quality)
    {
        return (saveImage(filename, "jpg", photo, quality));
    }
    
    public static boolean saveImage(final String filename, final String imageType, final Image photo, final float quality)
    {
        boolean saved = false;
        BufferedImage bi = new BufferedImage(photo.getWidth(null), photo.getHeight(null), BufferedImage.TYPE_INT_RGB);

        try
        {
            Iterator<ImageWriter> iter = ImageIO.getImageWritersByFormatName(imageType);
            ImageWriter writer = (ImageWriter)iter.next();
            // instantiate an ImageWriteParam object with default compression options
            
            ImageWriteParam iwp = writer.getDefaultWriteParam();
            
            if (iwp.canWriteCompressed())
            {            
                iwp.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
                iwp.setCompressionQuality(quality);   // a float between 0 and 1.  0 = best compression & worse quality, 1 = best quality & worst compression
                // 1 specifies minimum compression and maximum quality
            }
            
            File file = new File(filename);
            FileImageOutputStream output = new FileImageOutputStream(file);
            writer.setOutput(output);
            IIOImage image = new IIOImage(bi, null, null);
            writer.write(null, image, iwp);
            writer.dispose();
            
            saved = true;
        }
        catch (Exception ex)
        {
            System.out.println("Error saving JPEG : " + ex.getMessage());
        }

        return (saved);
    }    

regards,
CD

CreepingDeath

Note that the above implementation is independent of the Sun/Oracles JRE.
There is another way of implementing the above, but it relies on you using the Sun/Oracle JRE, so it may not work using other JRE's, eg. OpenJDK or IBM's JDK. But I'll add it here for completeness to show why I didn't use it in case someone posts it as a shorter/easier version.

 public static boolean saveJPEG(final String filename, final Image photo)
    {
        boolean saved = false;
        BufferedImage bi = new BufferedImage(photo.getWidth(null), photo.getHeight(null), BufferedImage.TYPE_INT_RGB);
        Graphics2D g2 = bi.createGraphics();
        g2.drawImage(photo, null, null);
        FileOutputStream out = null;

        try
        {
            out = new FileOutputStream(filename);
            JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
            JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(bi);
            param.setQuality(1.0f, false); // 100% high quality setting, no compression
            encoder.setJPEGEncodeParam(param);
            encoder.encode(bi);
            out.close();
            saved = true;
        }
        catch (Exception ex)
        {
            System.out.println("Error saving JPEG : " + ex.getMessage());
        }

        return (saved);
    }    

Nidge_Weasel

Hi Creeping death. I am aware of the image libraries, but the problem is I cannot use them, as I need to perform operations on the quantized DCT, and write them as a jpeg unchanged.

CreepingDeath

Nidge_Weasel wrote: »

Hi Creeping death. I am aware of the image libraries, but the problem is I cannot use them, as I need to perform operations on the quantized DCT, and write them as a jpeg unchanged.

Okay, I haven't done that, but this looks like it's in the right area.


http://alvinalexander.com/java/jwarehouse/mvnforum-1.0.0-rc4_04-src/myvietnam/src/net/myvietnam/mvncore/thirdparty/JpegEncoder.java.shtml

Nidge_Weasel

Can you believe, I found this before, but without the Huffman step working. This is perfect I think, thank you!