image - Why are my JPEG files larger than expected? -


gm convert +profile "*" -resize 800x800 -quality 90.0 -background white -flatten test.jpg test01.jpg

the test01.jpg file size 140262, test.jpg file size 114698, think test01.jpg file less test.jpg, why?

gm identify -verbose test.jpg command info: image: test.jpg   format: jpeg (joint photographic experts group jfif format)   geometry: 960x1280   class: directclass   type: true color   depth: 8 bits-per-pixel component   channel depths:     red:      8 bits     green:    8 bits     blue:     8 bits   channel statistics:     red:       minimum:                     0.00 (0.0000)       maximum:                   255.00 (1.0000)       mean:                      158.69 (0.6223)       standard deviation:         74.34 (0.2915)     green:       minimum:                     0.00 (0.0000)       maximum:                   255.00 (1.0000)       mean:                      142.36 (0.5583)       standard deviation:         72.48 (0.2842)     blue:       minimum:                     0.00 (0.0000)       maximum:                   255.00 (1.0000)       mean:                      105.80 (0.4149)       standard deviation:         73.05 (0.2865)   resolution: 72x72 pixels   filesize: 112.0ki   interlace: no   orientation: topleft   background color: white   border color: #dfdfdf   matte color: #bdbdbd   page geometry: 960x1280+0+0   compose: on   dispose: undefined   iterations: 0   compression: jpeg   jpeg-quality: 64   jpeg-colorspace: 2   jpeg-colorspace-name: rgb   jpeg-sampling-factors: 2x2,1x1,1x1   signature: ea09bde85095c8c8b2345e5301d581a8002490ecfefa63ae81c0cb14b8c2fbf8   profile-iptc: 40 bytes   profile-exif: 86 bytes     orientation: 1     exif offset: 38     color space: 1     exif image width: 960     exif image length: 1280   tainted: false   user time: 0.020u   elapsed time: 0:01   pixels per second: 39.1mi

enter image description here

according "identify" output presented input image "test.jpg", jpeg quality estimated 64. requested quality 90 output image.

higher quality means bigger filesize. increase in quality 64 90 doesn't improve visual quality of image; forces compressor faithfully reproduce compression artifacts in input image.


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