Technote Details :: Is the quality of my images preserved after upload?
Issue
What happens to the image quality when I upload it to the server and perform various alteration (e.g. upload and resize, crop, etc)? On some servers the modified images preserve quality, and on others not.
Reason
The quality is not stored in any type of image file, therefore when editing an image on the web server the original quality cannot be determined. Preserving quality depends on the image manipulation library that is used to perform the actual alteration.
Solution
The image manipulation algorithm in MX Kollection and KTML works as follows:
- When creating thumbnails from the original image, a loss of quality will occur. If using the GD library, generated thumbnails are in fact scaled images with a quality of 60. If using ImageMagick, the -thumbnail parameter is used, which removes some of the image components
- For all other image manipulation that need to have the quality defined, the quality factor is set to 80. Image manipulation libraries that try to preserve quality (e.g. ImageMagick) will use the default setting.
Note: The standard quality factor is 75, so when performing some image manipulation tasks you might even experience a minimal increase in the image quality. The quality factor is as defined for the IJG scale.
