Hi. Just wondering what option tweaks I might have available for image quality of JPG uploads through CMSB for a specific artist photographer client.
All of their uploaded images look great with 'Image Resizing Quality' set to 'Maximum' in Advanced Settings, but for a select batch of images, the quality of the resized image is not acceptable for either of us. There is an overall loss of crispness, resulting in the images looking out of focus/blurry. I think this may be due to the larger areas of solid color in these images, which doesn't translate as well when downsampled.
My question relates to the setting for '$quality' n the /lib/image_functions.php file. This looks like it might just be a speed value, but do you think a higher or lower value for this setting would produce a better image resolution?
Any suggestions for additional quality improvement short of manually sizing images and uploading them would be appreciated. All other uploads for all of my other clients are perfectly acceptable even at the mid-range setting. It's just these artsy images with solid areas of color that are iffy.
I found these notes in the image_functions.php library on the quality variable:
// Optional "quality" parameter (defaults is 3). Fractional values are allowed, for example 1.5. Must be greater than zero.
// Between 0 and 1 = Fast, but mosaic results, closer to 0 increases the mosaic effect.
// 1 = Up to 350 times faster. Poor results, looks very similar to imagecopyresized.
// 2 = Up to 95 times faster. Images appear a little sharp, some prefer this over a quality of 3.
// 3 = Up to 60 times faster. Will give high quality smooth results very close to imagecopyresampled, just faster.
// 4 = Up to 25 times faster. Almost identical to imagecopyresampled for most images.
// 5 = No speedup. Just uses imagecopyresampled, no advantage over imagecopyresampled.
I'd try updating the image $quality variable on line 64 of image_functions.php to 5 and see if that resolves the issue.
What file format are the images being uploaded in? I'd recommend trying different file types as well, for example large solid blocks of color are often rendered better in PNG format, while images with a lot of color gradients and contrast often look better in JPG format.
PHP Programmer - interactivetools.com
Greg, thanks so much for the suggestions.
I first tried changing the quality parameter to '5'. That helped, but almost imperceptibly so. I then saved the JPG as a PNG and uploaded it in that format, which helped more noticeably.