Differences in GD2 watermarked images quality in RC2 and RC3

[rbl]

Some users complained about significant differences in image quality between the beta site (RC2) and live site (RC3). So I've been doing some tests to see why the image quality dropped and found some disturbing results.
I use a small transparent 24bit PNG in the bottom right corner as a watermark.

The first and most important issue is the image quality after watermarking with GD2. A close inspection reveals lots of jpeg artifacts (mostly dots and texture like tissue) even with unchanged quality setting (-1).
So I tried several quality settings and there wasn't any difference between the images.
Just to be sure, I turn off watermarks and uploaded a few "big" pictures to test just the resize and not the watermark.

Conclusion is that changing settings works on RC2 but not on RC3.
Can anyone confirm?

Thanks!
Ricardo

Do you have your watermarking program set as GD1 or GD2?

[rbl]

Gd2

[paradise]

Yeah, I am having the same problem. After upgrading to RC3, the images started getting artifacts after uploading. Did not happen before RC3. Using GD2.

Try looking in your forum/includes/functions_gallery_imageedit.php file for this code:

Content visible to verified customers only.

Replace with this:

Content visible to verified customers only.

And let me know if that makes any difference.

[rbl]

No. It's still ignoring quality settings and outputting the image exactly the same.

I'm not exactly sure what would be causing it then. Would you mind submitting a support ticket so I can have a look?

[rbl]

Not at all but there's a catch, I'll send you a pm first.

[paradise]

Brian, here is an email that one of my members, who I asked to test it with three images, sent me (below) He compared :
1. Pre-upgrade image
2. Post upgrade but pre "your fix suggestion"
3. Post your suggestion.

ed, it is the same. what's happening is the files are being compressed. the first on i posted is 173.92 KB. now i upload the same photo and it is compressed to 30.18 KB. when i view it from my laptop lcd the image quality degradation is very obvious. but when i view it from my desktop monitor, it isn't as easy to notice. (that's because i have the contrast cranked all the way up and the darks are very dark)

[rbl]

Ok, in case someone finds this later, here's a follow up on this.

I submitted a ticket to Brian and after a few messages and tests, a possible solution was found although it may not fit everyone's shoe.

The way I see it, the problem is that you can't control the quality of the watermarked images. They are always generated with the same quality setting and in some images, the jpeg artifacts are very noticeable.
So I thought we could use the "Original image quality" setting in vBa Gallery -> Modify Settings. This value is used to set the quality of resized images per category.

To try it, open your forum/includes/functions_gallery_imageedit.php, look for the line
@imagejpeg($mainimage, iif($perm, $imglocation, ''), -1);
in funtion watermark_image, and replace it with:
@imagejpeg($mainimage, iif($perm, $imglocation, ''), $catoptions["$imageinfo[catid]"]['gallery_origquality']);

The difference is huge but we'll get to that later.
Regarding this solution, Brian warned that "setting the quality for watermarks to 100 is going to create files about twice the size as the original, which is why -1 has been hardcoded into the script in RC3. Just using the quality setting for original images wouldn't be a good solution for most because if you set the quality to 50 it's first going to change the quality of the original image to 50, then change the quality again when it watermarks the image, so you'd end up with an image with a quality of 25."

On my site, I've set the quality to 90 (or 95). The image size gain is not significant and I do prefer sacrifice space than quality but that's my call. You might prefer the opposite!

To give an example, my test image has 105KB on my disk, but with quality set to 100, it jumps to a whooping 194KB on Gallery.
Setting quality to 95, the size in Gallery is 120KB which I think is a good size/quality ratio.
Be warned, your millage may vary. Make a few tests first.