Image compression?

[rlam3]

Is there a way to compress the image size but not resolution?

Similar to http://stackoverflow.com/questions/21920028/how-does-python-pil-and-pillow-compress-pictures

[emcconville]

You can use wand.image.BaseImage.compression_quality to match PIL's quality, and wand.image.BaseImage.resolution for dpi.

Example...

from wand.image import Image

with Image(filename="input.jpg") as image:
    image.compression_quality = 90
    image.resolution = (300, 300)
    image.save(filename="output.jpg")

[xmedeko]

The compression_quality does not work for me for PNG image:

with Image(filename='input.png') as img:
    img.compression_quality = 95
    img.save(filename=self.tmp_filename('output.png'))

The result is same does not matter which compression_quality I set. From commandline convert input.png -quality 95 output.png it works - I see different file size.

Update: solution is to use: MagickSetCompressionQuality (ImageMagick releases after 6.8.7-5) instead of MagickSetImageCompressionQuality (ImageMagick releases before 6.8.7-5), see:

• Image compression not working on some png images. ImageMagick/ImageMagick#29 (comment)
• https://stackoverflow.com/a/34618887/254109

[emcconville]

Setting Image.compression_quality now sets both image & image info properties on MagickWand instances