Apng with region clearing

[marcos-dogonahorse]

hi Aellerton,

I notice a bug while working with your wrapper around japng. It seems in the latest code, you clear the whole screen every time the FrameController return a 1 in the disposeOP ( PngAnimationComposer.java -> function completeFrame(Argb8888Bitmap frameImage) )

The problem with that is that there are images that depend on the previous screen being only partly clear. These reduces the png file size and is completely supported by the APNG standers ( https://developer.mozilla.org/en-US/docs/Mozilla/Tech/APNG#.27fcTL.27:_The_Frame_Control_Chunk
)

The solution to that problem is that you always only clear the region of the next frame.

so this should be the new switch statement in that function:

switch (currentFrame.disposeOp) {
            case 1: // APNG_DISPOSE_OP_BACKGROUND
                Rect region = new Rect(currentFrame.xOffset, currentFrame.yOffset, currentFrame.xOffset + currentFrame.width, currentFrame.yOffset + currentFrame.height);
                canvas.drawRect(region, clearModePaint);
                break;
            case 2: // APNG_DISPOSE_OP_PREVIOUS
                //System.out.println(String.format("Frame %d restore previous (full=%s, x=%d y=%d w=%d h=%d) previous=%s", currentFrame.sequenceNumber,
                //        isFull, currentFrame.xOffset, currentFrame.yOffset, currentFrame.width, currentFrame.height, previous));

                // Put the original section back
                if (null != previous) {
                    //paint = new Paint();
                    //paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));
                    paint = srcModePaint;
                    canvas.drawBitmap(previous, currentFrame.xOffset, currentFrame.yOffset, paint);

                    //System.out.println("  Restored previous "+previous.getWidth()+" x "+previous.getHeight());
                    previous.recycle();
                } else {
                    System.out.println("  Huh, no previous?");
                }
                break;

            case 0: // APNG_DISPOSE_OP_NONE
            default: // Default should never happen
                // do nothing
                //System.out.println("Frame "+currentFrame.sequenceNumber+" do nothing dispose");
                break;

        }

clearModePaint is just a paint that i store from the constructor
this.clearModePaint = new Paint(); this.clearModePaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));

Here is an sample image that you can see the problem in:

Thank you again for the wrapper 👍

[aellerton]

Thanks so much for this bug report - it makes total sense. I'm not able to work on the code for a couple weeks as I'm travelling but I will get to it (promise!). Alternatively, I welcome PRs. :) Thanks again!

…

On 12 Apr 2017 5:17 pm, "marcos-dogonahorse" ***@***.***> wrote: hi Aellerton, I notice a bug while working with your wrapper around japng. It seems in the latest code, you clear the whole screen every time the FrameController return a 1 in the disposeOP ( PngAnimationComposer.java -> function completeFrame(Argb8888Bitmap frameImage) ) The problem with that is that there are images that depend on the previous screen being only partly clear. These reduces the png file size and is completely supported by the APNG standers ( https://developer.mozilla.org/ en-US/docs/Mozilla/Tech/APNG#.27fcTL.27:_The_Frame_Control_Chunk ) The solution to that problem is that you always only clear the region of the next frame. so this should be the new switch statement in that function: ` switch (currentFrame.disposeOp) { case 1: // APNG_DISPOSE_OP_BACKGROUND Rect region = new Rect(currentFrame.xOffset, currentFrame.yOffset, currentFrame.xOffset + currentFrame.width, currentFrame.yOffset + currentFrame.height); canvas.drawRect(region, clearModePaint); break; case 2: // APNG_DISPOSE_OP_PREVIOUS //System.out.println(String.format("Frame %d restore previous (full=%s, x=%d y=%d w=%d h=%d) previous=%s", currentFrame.sequenceNumber, // isFull, currentFrame.xOffset, currentFrame.yOffset, currentFrame.width, currentFrame.height, previous)); // Put the original section back if (null != previous) { //paint = new Paint(); //paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC)); paint = srcModePaint; canvas.drawBitmap(previous, currentFrame.xOffset, currentFrame.yOffset, paint); //System.out.println(" Restored previous "+previous.getWidth()+" x "+previous.getHeight()); previous.recycle(); } else { System.out.println(" Huh, no previous?"); } break; case 0: // APNG_DISPOSE_OP_NONE default: // Default should never happen // do nothing //System.out.println("Frame "+currentFrame.sequenceNumber+" do nothing dispose"); break; } ` clearModePaint is just a paint that i store from the constructor this.clearModePaint = new Paint(); this.clearModePaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR)); Here is an sample image that you can see the problem in: [image: 12338-img-l-1491582573446 w400] <https://cloud.githubusercontent.com/assets/13003036/24979875/e658e7c8-1fa3-11e7-908a-f1a201d38d52.png> Thank you again for the wrapper 👍 — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#3>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AA7EolHhPVTY1mCKSWnr72iNVQOur6bqks5rvT-AgaJpZM4M7-5r> .