Legacy ImageMagick Discussions Archive

I'm using RMagick for this.

I'm resizing JPEGs that were saved via Photoshop's "Save for web" with a quality of 10. When I resize the image to one with a smaller resolution the resulting file is much larger than the original.

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[jkat@localhost resize-test]$ cat resize.rb 
#!/usr/bin/ruby
require 'RMagick'

img = Magick::ImageList.new(ARGV.shift).first
img.change_geometry("1000x") do |cols, rows, i|
  i.resize!(cols, rows) 
  i.write('A.jpg')          
end

[jkat@localhost resize-test]$ !.
./resize.rb product-10.jpg 

[jkat@localhost resize-test]$ !iden
identify product-10.jpg A.jpg 
product-10.jpg JPEG 1486x2000 1486x2000+0+0 8-bit DirectClass 220kb 
A.jpg[1] JPEG 1000x1346 1000x1346+0+0 8-bit DirectClass 443kb

I tried playing around with:

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img.distort(Magick::ScaleRotateTranslateDistortion, ...)

but it did not help.

How can I reduce the resized image's size. I'd hope it could be smaller the than original.

Also

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identify -verbose product-10.jpg A.jpg

produce nearly identical output (except for APP12 profile in product).

I think what is happening is that ImageMagick by default uses a quality of 85 (best is 100) when it saves a JPG so you may be saving the smaller image at a much higher quality than the original. I don't know how to do this with RMagick but just before you write the JPG you need to set the JPG compression quality to a lower value. There seems to be an example of specifying the compression here:
http://www.imagemagick.org/RMagick/doc/ ... ompressing

Pete

Yes that was it, thanks. A pretty obvious solution but the docs (bundled with RMagick gem) are lacking.

Legacy ImageMagick Discussions Archive

Resized File Has Smaller Resolution But Much Larger Size

Resized File Has Smaller Resolution But Much Larger Size

Re: Resized File Has Smaller Resolution But Much Larger Size

Re: Resized File Has Smaller Resolution But Much Larger Size