If this is done via cutting the resolution of the image down a bit, or increasing the jpeg compression then it is fine. I am basically looking for the most compression I can get without any visible notice in image degradation.

These are mostly white comic book panels an example of which can be found here: (be aware that I don't know if the host compresses or modifies the images uploaded). The black and white images that make up 98% of the images:ī.jpg JPEG 2037x3056 2037x3056+0+0 8-bit Gray 256c 1.201MB 0.063u 0:00.070ĭ.jpg JPEG 1200x1800 1200x1800+0+0 8-bit sRGB 39.9KB 0.016u 0:00.012įrom this I gather that any images of color are using the sRGB profile, and any of the main content is using a Gray profile.Īfter running convert with -strip I don't see any diference in quality, but the file size actually increased:Īa.jpg JPEG 2037x3056 2037x3056+0+0 8-bit sRGB 1.987MB 0.000u 0:00.000Īny other information you might require for aiding me in this topic? You should also check your quality values to be sure you do not already have too low a quality value. You should test on a few images using convert/magick (depending upon whether you use IM 6 or IM 7) to see the effects of -strip. I would suggest you convert all files to sRGB with profiles. But you need to be careful or test if the JPG files are CMYK or sRGB before doing the latter.

So you may want to be careful about that or reset your color profiles after doing a -strip. strip will remove most meta data including profiles. You can use mogrify to process a whole directory of images. But if you want 'the least reduction that meets some criteria', that would have to be scripted.Īny script that processed images differently would use 'magick' or 'convert', not 'mogrify'. This can be done in a script or compiled program. IM has no command to 'reduce JPEG quality to give the most compression within a maximum 1% change'. Personally, I find a 1% RMSE change to ordinary photographs is usually invisible.

Changes (by definition) lower the quality, but you might find a small amount of change to be acceptable. The greater the compression, the greater the change. JPEG is lossy compression, so it changes images. I suppose these are photographs? Or, at any rate, like photos? How much do ou want to compress them by? Put this in a shell loop to do subdirectories. 'Mogrify' can process the files (possibly with wildcards) in a directory, processing all files in the same way. I suppose you want all results to be encoded as sRGB. Which applications of the imagemagick suite is suitable for this batch task and how can I add this recursive behavior so that it applies to all images from a base directory and sub directories?Īs Fred says, especially the caution on stripping profiles. All image must maintain the same resolution ratio. If 2) is not feasible then a reduction of the file dimensions (shrinking to a new resolution) would take priority over reducing image quality. The images are black and white except for maybe about 150 which are color.ġ) convert all files that are not jpg to jpgĢ) reduce the file size of all images without reducing quality or image dimensions (I heard the -strip option might reduce the file size a lot without impacting quality) The images are mostly the same size (dimensions) most of which are 2037x3056, the next most being 4074x3056, and finally there are a few at 1200x1800. The 4000 images are broken up into groups each group having it's own directory within the parent directory. Most are jpg but there may be the a few png scattered throughout. I have 4000 images that total 8.9gb in size.

Image file size reducer php