Legacy ImageMagick Discussions Archive

In IrfanView JPEG saving options dialogue, there is checkbox "disable color subsampling", and in Corel PhotoPaint, there is "jpeg sub-format" selector with "4:2:2" and "4:4:4" options.

If "disable subsampling" checked, or "4:4:4" selected, JPEGs with the same quality became little bigger, but some colors (especially reds) looks closer to original.

How can I reproduce same result with ImageMagick?
Is it correct to use -sampling-factor 4:4:4 ?
Which is default value, 4:2:2 ?

Use a combination of -quality and -sampling-factor to increase quality of the JPEG image. Try

• -quality 100 -sampling-factor 1:1:1

and work backwards from there until you reach a compromise between image fidelity and image compression size.