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Convert images from Windows Batch script
Posted: 2018-01-29T19:45:49-07:00
by moet36
Hi
This is my first post here, so hope my questions is ok.
We use Imagemagick for batch processing images before using them on our website.
We currently use the following:
convert input.jpg -resize 1300x1300 -quality 60 -strip -colorspace sRGB output.jpg
Our images come in various formats. Our website is optimized for handling images with proportions 3:2 in both landscape and portrait format, i.e. 1300x867 and 867x1300.
I would like to automate so that all images are automatically resized to have this proportion of 3:2 (it should cut off equally in top/bottom or left/right when cropping). Not sure if Imagemagick can figure out whether it is supposed to be an portrait image (height > width) or landscape image (width > height) and then make the crop to the 3:2 (or 2:3) format accordingly and after that resize to have a max width/height of 1300 px ?
Can anyone help ?
Thank you in advance
Re: Convert images from Windows Batch script
Posted: 2018-01-29T20:06:51-07:00
by fmw42
Please alway identify your version of ImageMagick as some syntax difference occur between IM 6 and IM 7
Re: Convert images from Windows Batch script
Posted: 2018-01-29T20:52:13-07:00
by fmw42
If using IM 6.9.9.34 or IM 7.0.7-22, then there is a new feature in -crop that allows cropping to a given aspect ratio. You first have to decide if portrait or landscape. You can do that with
Code: Select all
convert image -format "%[fx:(w>h)?1:0]" info:
1 means landscape and 0 means portrait
The do a conditional test. That code is OS dependent for its syntax. I just use pseudo code here for the conditional
Code: Select all
if 1 (landscape); then
convert input.jpg -resize 1300x1300 -quality 60 -strip -colorspace sRGB -gravity center -crop 3:2+0+0 +repage output.jpg
else (portrait); then
convert input.jpg -resize 1300x1300 -quality 60 -strip -colorspace sRGB -gravity center -crop 2:3+0+0 +repage output.jpg
Otherwise, it becomes a bit more complicated, but can be done with more scripting.
Re: Convert images from Windows Batch script
Posted: 2018-01-29T21:32:11-07:00
by GeeMack
moet36 wrote: ↑2018-01-29T19:45:49-07:00I would like to automate so that all images are automatically resized to have this proportion of 3:2 (it should cut off equally in top/bottom or left/right when cropping). Not sure if Imagemagick can figure out whether it is supposed to be an portrait image (height > width) or landscape image (width > height) and then make the crop to the 3:2 (or 2:3) format accordingly and after that resize to have a max width/height of 1300 px ?
Using IM6 on Windows 10 I worked up a command to crop an image to the largest output image of aspect ratio 3:2, or 2:3 if the input has a vertical orientation.
Code: Select all
convert input.png -write mpr:input ^
-set option:distort:viewport "%%[fx:w<h&&w/2>h/3?h/3*2:w]x%%[h]" -distort SRT 0 ^
-set option:distort:viewport "%%[fx:w>h&&w/3>h/2?h/2*3:w]x%%[h]" -distort SRT 0 ^
-set option:distort:viewport "%%[w]x%%[fx:w<h&&w/2<h/3?w/2*3:h]" -distort SRT 0 ^
-set option:distort:viewport "%%[w]x%%[fx:w>=h&&w/3<h/2?w/3*2:h]" -distort SRT 0 ^
mpr:input +repage -gravity center -composite output.png
That reads the input image and stores a copy in the memory register "mpr:input". Next it does a series of tests and viewport resizing to create the required 3:2 or 2:3 canvas. Then it brings that saved input image back and composites it centered over the proportioned canvas. The result is as if you cropped the largest 3:2 (or 2:3) proportioned area from the center of the input.
A square input will be output as a horizontal 3:2 image.
Any other operators for resizing etc. can be added before the final output. If you "-resize 1300x1300" the output will keep its 3:2 (or 2:3) proportions and be limited to 1300 pixels in the longer direction.
The command is written for a BAT file. To use it at the command line you'd have to change all the double percent signs "%%" into singles "%".