I've dug a little deeper, and problem persists.
I went into processing source of PImage and found out that htese errors are not coming from Processing. In fact I mass-searched all source files and didn't find any reference of 'Huffman' codes. I think Processing is using Java libraries for dealing with JPG's and they are hiding my errors.
Here's the full code so anybody can try it to see the results. It corrupts a JPG (in memory, never touches the file) and shows the result. I want to catch any errors with JPEG compression so I can undo the last change and try another, effectively making sure it is always displayable. If you run the following, (you need an image.jpg in your data folder) you'll see errors pop up eventually that are not inside my Exception branch. I made the section that I suspect of being the culprit bold, but I'm not sure.
You'll see the picture slowly (or rapidly, depending on size and compression) get visually corrupted.
This is the desired effect. I just want to know when the data gets so messed up that it can't be displayed or is displayed black/grey.
- import java.io.File;
- import java.awt.Toolkit;
- import java.awt.MediaTracker;
- PImage i;
- int k =1;
- byte b[];
- void setup()
- {
- frameRate(5);
- size(1000, 1000);
- b = loadBytes("image.jpg");
- }
- void draw()
- {
- corrupt();
- }
- void corrupt()
- {
- try {
- Image rawImg = Toolkit.getDefaultToolkit().createImage(b);
- PImage img = my_image_loader(rawImg);
- image(img, 0, 0);
- int r = round(random(0, b.length-1));
- byte flipbit = (byte) (1 << round(random(0, 7)));
- if (b[r]>= flipbit) {
- b[r] -= flipbit;
- }
- else {
- b[r] += flipbit;
- }
- }
- catch (Exception e) {
- println("Error anywhere");
- println(e.getStackTrace());
- }
- }
- PImage my_image_loader(Image awtImage) {
- MediaTracker tracker = new MediaTracker(this);
- tracker.addImage(awtImage, 0);
- try {
- tracker.waitForAll();
- }
- catch (Exception e) {
- println("Error in the img loader");
- println(e.getStackTrace());
- }
- PImage image = new PImage(awtImage);
- image.parent = this;
- return image;
- }
The
my_image_loader is copied from the
loadImageMT in
PApplet.java.
-
protected PImage loadImageMT(Image awtImage) {
-
MediaTracker tracker = new MediaTracker(this);
-
tracker.addImage(awtImage, 0);
-
try {
-
tracker.waitForAll();
-
} catch (InterruptedException e) {
-
//e.printStackTrace(); // non-fatal, right?
-
}
-
PImage image = new PImage(awtImage);
-
image.parent = this;
-
return image;
-
}
