Setting GD's JPEG compression quality

dersmon · June 10, 2022, 9:01am

When uploading cover images, they get downscaled as thumbnails. The quality is rather low causing a lot of artefacts. Is there a way to set the default compression quality?

rcgillis · June 10, 2022, 11:53am

Hi @dersmon,

Can you please indicate which version of PKP software (e.g. OJS, OMP 3.3.0-8) you’re using?

-Roger
PKP Team

dersmon · June 13, 2022, 6:55am

Hey!

We are currently running OMP 3.1.2.

Regards,
Simon

rcgillis · June 13, 2022, 1:40pm

Hello @dersmon,

I ran this by our developers, who had this to say:

I’ve just skimmed the code and it’s using the default quality (around 75 in a scale from 0 - 100).
At this moment, there’s no way to change it without updating the code, we could have a generic setting for this. The above applies to jpg files… Other formats might have other defaults or no quality setting at all

Here’s the place in the code that the quality for JPGs can be set:

github.com

pkp/omp/blob/stable-3_3_0/classes/services/PublicationService.inc.php#L538


      
          
          			// Choose the smallest ratio and create the target.
          			$ratio = min($xRatio, $yRatio);
          
          			$thumbWidth = round($ratio * $originalSizeArray[0]);
          			$thumbHeight = round($ratio * $originalSizeArray[1]);
          			$thumb = imagecreatetruecolor($thumbWidth, $thumbHeight);
          			imagecopyresampled($thumb, $cover, 0, 0, 0, 0, $thumbWidth, $thumbHeight, $originalSizeArray[0], $originalSizeArray[1]);
          
          			switch ($pathParts['extension']) {
          				case 'jpg': imagejpeg($thumb, $thumbFilePath); break;
          				case 'png': imagepng($thumb, $thumbFilePath); break;
          				case 'gif': imagegif($thumb, $thumbFilePath); break;
          				case 'webp': imagewebp($thumb, $thumbFilePath); break;
          			}
          
          			imagedestroy($thumb);
          		}
          
          	}
          }

I should note, however, that this is for version 3.3. The version that you’re using is out of date - and I would highly recommend upgrading.

We also discussed the possibility of this may be a setting within OJS that could be done without having to modify the code. To that end, I’ve flagged this post as a “Feature Request” so our developers can discuss the feasibility of this.

-Roger
PKP team

dersmon · June 14, 2022, 11:55am

Thank you for checking with the developers. A setting would be nice indeed, it is most notable with single colour covers that have a fiber material.