ImageMagick: resize image and reduce file size [closed]

Question

Using ImageMagick, I'm trying to resize a JPEG's dimensions and reduce the file size.

The issue is that I don't want to worsen the image quality.

I've tried the following commands:

convert -resize 170x80 -resample 100x100 image1.jpg image2.jpg

=> A resized picture but with bad quality.

convert -resize 170x80 -quality JPEG image1.jpg image2.jpg

=> A resized image and with good quality, but the same file size.

convert -density 600 -resize 170x80 image1.jpg image2.jpg

=> A resized image but very bad quality.

I don't know what option I should use.

Answer 1

quality parameter has a numeric value. From -quality doc :

For the JPEG and MPEG image formats, quality is 1 (lowest image quality and highest compression) to 100 (best quality but least effective compression). The default is to use the estimated quality of your input image if it can be determined, otherwise 92.

You may use quality lower than the default 92 to reduce the size, e.g. 72 as:

convert -resize 170x80 -quality 72 image1.jpg image2.jpg