Resize jpeg fast

Question

Hi Guys
I have the following code that I use to get a picture in the format of a byteArray[] into an ImageObject, in order to be able to resize the picture into a thumbnail.
Image inImage = new ImageIcon(pictureAsByteArray).getImage();
The problem is that the creation of the Image object takes way too long!! Is there a better way to do this?
Thanks
David

Answer 1

Well, I dont know what types of images you plan on using, but I was working with XWD (X-windows dump) images. The XWDs are filled up with header information first and then the pixel bytes come next (I would assume it's the same setup with every other type of image). So, I retrieved the image width and height information from the header. Then, I have my own size constants THUMBNAIL_WIDTH and THUMBNAIL_HEIGHT that I want the thumbnails to be. I make some other variables like the reduced ratio of the image, the pixel array of my resulting image, and the number of pixels I create per every row.
int RATIO = header.windowHeight/THUMBNAIL_HEIGHT;
int[] pixels = new int[(header.pixmapWidth/RATIO) * (header.pixmapHeight/RATIO)];
int valsPerRow = header.pixmapWidth/RATIO;// # of used pixels per row
int count = 0, rowCount = 0;Then it's only a matter of a simple loop.
for (int pixelCount = 0; pixelCount < pixels.length; pixelCount++) {
                pixels[pixelCount] = 0;
                rowCount = pixelCount/valsPerRow;
                if (pixelCount%valsPerRow == 0)
                    count = RATIO * rowCount * header.bytesPerLine;
                // do some stuff to obtain RGB values from the bytes
                pixels[pixelCount]= //add up RGB to make single pixel 
                count = count + RATIO*bytesPerPixel; 
            }// for   The hardest part was obtaining the proper RGB values from the bytes (had to worry about Big Endian/Little Endian byte order and all these Unix boxes creating their screen dumps in a different way).
By the way, does anyone know of a good algorithm for reading all types of X-windows dump images (X11 only, dont need X10)?
My own algorithm works for the most part, but even though I tried to make it as general as possible, I still have too many exception cases and have discovered some images that still dont look right. Although, many programs that claim to view XWDs also screw up, but GIMP seems to be able to view them all. I wish they would release their algorithm for reading XWDs, because I get the feeling there is something tricky there that I just dont know about.
I hope I'm not the only one that had to read in XWDs into Java...
Val