[RESOLVED] Possible to control PNG Quality?

partypete

Hello,

When resizing PNG images with PHP, is there any way to control it's quality? I didn't see any. Right now the smaller resized image is 129KB and the original bigger image is only 45KB. The size almost tripled even though the image was made smaller.

Does PHP have any abilities that I might have missed that can help control quality/file size of PNGs?

Thanks,
Peter

bradgrafelman

Depends on what you're doing to resize the images. If you're using the GD library, make sure you're using these functions: [man]imagecreatetrucolor/man and [man]imagecopyresampled/man.

partypete

Thanks for the reply. Yes I am using those. Was hoping there might be some kind of quality setting for png like there is when saving jpegs.

Weedpacket

Not really, because PNG is a lossless compression format, so it's not going to start throwing information out to sacrifice image quality for compactness. What you have got are choices between truecolour or various palette sizes. The original image was palette-based? If the smaller image uses truecolour (which it would be if you're using imagecreatetruecolor), then that would make a significant difference. Between imagecreate/imagecreatetruecolor and imagecopyresized/imagecopyresampled, there are four possible combinations to play with. You could use imagecopypalette() or imagetruecolortopalette() also.

partypete

Great Weedpacket! I didn't think there would be a quality(compression) feature like jpegs, but was thinking there might be an option to limit colours or something. Looks like you've given me some good leads... will read up on imagecopypalette, imagetruecolortopalette and the others you mentioned.

Thanks!
Peter