Re: Basic question (generating thumbnails)

Posted by Wayne Rasband on May 30, 2006; 9:30pm
URL: http://imagej.273.s1.nabble.com/Basic-question-tp3702635p3702636.html

Try upgrading to ImageJ 1.37b or later. It averages source pixels when
RGB images are reduced by more than 4:1, resulting in better looking
thumbnails. It also helps to enhance the contrast, which you can do
using something like

     (new ContrastEnhancer()).stretchHistogram(imp2, 0.05);

or like this in a macro

    run("Enhance Contrast", "saturated=0.05");

-wayne


On May 30, 2006, at 11:04 AM, TDLN wrote:

> I recently switched from using javax.imageio to ImageJ and I am
> running into several basic issues. I hope some of you can help me out.
>
> The requirements are a multi threaded webcrawler that is generating
> thumbnails from URL's to Image files (jpg, png and gif). The
> thumbnails are written to a predefined directory on the file system.
> Thumbnails should be 100px*100px; we need the best possible quality.
> File size of the generated thumbails is not so important. Performance
> is crucial though. Processing should be done in the backgroung (no
> gui).
>
> I started with this code.
>
> ImagePlus ip = new ImagePlus(imageUrl);
> ImageProcessor imp = ip.getProcessor();
> ImageProcessor imp2 = imp.resize(THUMB_WIDTH, THUMB_HEIGHT);
> imp2.setInterpolate(true);
> ImagePlus ip2 = new ImagePlus("Resized Image", imp2);
> FileSaver fs = new FileSaver(ip2);
> JpegWriter.setQuality(100);
> fs.saveAsJpeg();
>
> Performance is OK, but the quality of the generated thumbnails is not
> so good.
>
> Then I read this thread that has some info on improving the quality of
> the generated thumbnails:
> https://list.nih.gov/cgi-bin/wa?A2=ind0512&L=IMAGEJ&P=R2440&I=-3
>
> I tried both IJ.run("","") and IJ.runMacro(String macro) style syntax.
>
> Both give me different types of errors:
>
> - Image locked errors
> - A window pops up and no thumbnail is generated
> - Runtime exceptions
>
> Some thumbs are generated though and they are much better quality than
> before, reason I like to ge this code working.
>
> Now, I think my problems are related to threading issues. I am very
> new to ImageJ and probably my question shows my basic ignorance. Still
> I hope some of you read so far and can give me some hints or pointers
> to some examples.
>
> Rgrds. Thomas Delnoij
>