Crop a large image into multiple smaller ones

[fmw42]

you need to specify the -quality setting for your jpg output file. IM uses a default of -quality 80. Your input image may have been at a lower quality than the outputs using the default quality of 80. You can set it lower if you want smaller jpg file sizes. Also add +repage to your command. Also put your input image right after "convert".

convert big_file -crop 120x120 -quality 50 +repage small_file.jpeg

[anthony]

Jpg is not recommended as a intermediate image, only as a final image format for use on the web. If you can try and keep a copy of images in a non-lossy format like PNG (yes it is larger), or better still always try to start processing image from the original source image so ac to avoid loss of quality.