Recommendation for compressing JPG files with ImageMagick

Question

I want to compress a JPG image file with ImageMagick but can t get much difference in size  By default the output size is bigger than the input  I don t know why  but after adding some  profile options and setting down the quality I can get an smaller size but still similar to original   The input image is 255kb  the processed image is 264kb  using  profile to remove profiles and setting quality to 70    Is there any way to compress that image to 150kb at least  Is that possible  What ImageMagick options can I use

User · Answer

Did some experimenting myself here and boy does that Gaussian blur make a nice different. The final command I used was:

mogrify * -sampling-factor 4:2:0 -strip -quality 88 -interlace Plane -define jpeg:dct-method=float -colorspace RGB -gaussian-blur 0.05

Without the Gaussian blur at 0.05 it was around 261kb, with it it was around 171KB for the image I was testing on. The visual difference on a 1440p monitor with a large complex image is not noticeable until you zoom way way in.

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JavisPerez -- Is there any way to compress that image to 150kb at least  Is that   possible  What ImageMagick options can I use    See the following links where there is an option in ImageMagick to specify the desired output file size for writing to JPG files   http   www imagemagick org Usage formats  jpg write http   www imagemagick org script command-line-options php define  -define jpeg extent  size  As of IM v6 5 8-2 you can specify a maximum output filesize for the JPEG image  The size is specified with a suffix  For example  400kb    convert image jpg -define jpeg extent 150kb result jpg   You will lose some quality by decompressing and recompressing in addition to any loss due to lowering -quality value from the input

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I would add an useful side note and a general suggestion to minimize JPG and PNG   First of all  ImageMagick reads  or better  guess      the input jpeg compression level and so if you don t add -quality NN at all  the output should use the same level as input  Sometimes could be an important feature  Otherwise the default level is -quality 92  see www imagemagick org   The suggestion is about a really awesome free tool ImageOptim  also for batch process  You can get smaller jpgs  and pngs as well  especially after the use of the free ImageAlpha  not batch process  or the free Pngyu if you need batch process   Not only  these tools are for Mac and Win and as Command Line  I suggest installing using Brew and then searching in Brew formulas

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I use always   quality in 85 progressive  comprobed compression  a very tiny gausssian blur to optimize the size  0 05 or 0 5 of radius  depends on the quality and size of the picture  this notably optimizes the size of the jpeg  Strip any comment or EXIF metadata  in imagemagick should be convert -strip -interlace Plane -gaussian-blur 0 05 -quality 85  source jpg result jpg  or in the newer version  magick source jpg -strip -interlace Plane -gaussian-blur 0 05 -quality 85  result jpg  Source  From  Fordi in the comments  Don t forget to upvote him if you like this   If you dislike blurring  use -sampling-factor 4 2 0 instead  What this does is reduce the chroma channel s resolution to half  without messing with the luminance resolution that your eyes latch onto  If you want better fidelity in the conversion  you can get a slight improvement without an increase in filesize by specifying -define jpeg dct-method float - that is  use the more accurate floating point discrete cosine transform  rather than the default fast integer version

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If the image has big dimenssions is hard to get good results without resizing  below is a 60 percent resizing which for most of the purposes doesn t destroys too much of the image   I use this with good result for gray-scale images  I convert from PNG     ls     png   xargs -L1 -I    convert    -strip -interlace JPEG -sampling-factor 4 2 0 -adaptive-resize 60    -gaussian-blur 0 05 -colorspace Gray -quality 20     jpg   I use this for scanned B amp W pages get them to gray-scale images  the extra arguments cleans shadows from previous pages     ls     png   xargs -L1 -I    convert    -strip -interlace JPEG -sampling-factor 4 2 0 -adaptive-resize 60    -gaussian-blur 0 05 -colorspace Gray -quality 20 -density 300 -fill white -fuzz 40   opaque   000000  -density 300    jpg    I use this for color images   ls     png   xargs -L1 -I    convert    -strip -interlace JPEG -sampling-factor 4 2 0 -adaptive-resize 60    -gaussian-blur 0 05 -colorspace RGB -quality 20     jpg

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I m using the Google Pagespeed Insights image optimization guidelines  and for ImageMagick they recommend the following   -sampling-factor 4 2 0    -strip    -quality 85  it can vary  I use range 60-80  lower number here means smaller file     -interlace    -colorspace RGB  Command in ImageMagick   convert image jpg -sampling-factor 4 2 0 -strip -quality 85 -interlace JPEG -colorspace RGB image converted jpg   With these options I get up to 40  savings in JPEG size without much visible loss

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Once I needed to resize photos from camera for developing    Original filesize  2800 kB Resolution  3264x2448   Command   mogrify -quality  97   -resize 2048x2048 -filter Lanczos -interlace Plane -gaussian-blur 0 05     Result filesize 753 kB Resolution 2048x2048   and I can t see any changes in full screen with my 1920x1080 resolution monitor  2048 resolution is the best for developing 10 cm photos at maximum quality of 360 dpi  I don t want to strip it   edit  I noticed that I even get much better results without blurring  Without blurring filesize is 50  of original  but quality is better  when zooming

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Here s a complete solution for those using Imagick in PHP    im   new  Imagick  filePath    im- gt setImageCompression  Imagick  COMPRESSION JPEG    im- gt setImageCompressionQuality 85    im- gt stripImage     im- gt setInterlaceScheme  Imagick  INTERLACE PLANE       Try between 0 or 5 radius  If you find radius of 5     produces too blurry  pictures decrease to 0 until you     find a good balance between size and quality    im- gt gaussianBlurImage 0 05  5         Include this part if you also want to specify a maximum size for the images   size    im- gt getImageGeometry     maxWidth   1920   maxHeight   1080       ----------                  ---------- if  size  width    gt    size  height       if  size  width    gt   maxWidth        im- gt resizeImage  maxWidth  0   Imagick  FILTER LANCZOS  1              ------                                            ------ else    if  size  height    gt   maxHeight        im- gt resizeImage 0   maxHeight   Imagick  FILTER LANCZOS  1

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I added -adaptive-resize 60  to the suggested command  but with -quality 60    convert -strip -interlace Plane -gaussian-blur 0 05 -quality 60  -adaptive-resize 60  img original jpg img resize jpg   These were my results   img original jpg   13 913KB   img resized jpg   845KB   I m not sure if that conversion destroys my image too much  but I honestly didn t think my conversion looked like crap  It was a wide angle panorama and I didn t care for meticulous obstruction

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Just saying for those who using Imagick class in PHP    im - gt  gaussianBlurImage 0 8  10          blur  im - gt  setImageCompressionQuality 85      set compress quality to 85

[image-processing] Recommendation for compressing JPG files with ImageMagick

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