ImageMagick is widely used in industries such as web development, graphic design, and video editing, as well as in scientific research, medical imaging, and astronomy. The two most common commands are mogrify and convert, where mogrify overwrites the existing image and convert saves the image as a new image without modifying the original image. It can be used to create, edit, compose, or convert bitmap images, and supports a wide range of file formats, including JPEG, PNG, GIF, TIFF, and PDF. The following command takes a PNG file named 'howtogeek.png' in the current directory and creates a JPEG image from it: convert howtogeek.png howtogeek.jpg You can also specify a compression level for JPEG images: convert howtogeek.png -quality 95 howtogeek.jpg The number must be between 1 and 100. If ImageMagick is not pre-installed on your system you can follow the installation instructions which are pretty straight forward for the various operating systems. magick hald3.png ( +clone -sepia-tone 60 ) -evaluate-sequence mean haldsepia.png magick rose.png haldsepia.png -hald-clut rosehaldsepia. The various command-line tools can be seen in the documentation and their usage can be seen in the examples. It can be incorporated into shell scripts, batch files or through other programs for automatic processing of images. ImageMagick can do a lot of different graphics editing tasks and it even can create new images from the command-line. ![]() Here I’ll introduce a few common commands I had to look up multiple times. One tool I commonly use in these desperate situations is ImageMagick, which is a powerful tool when automating raster and vector image processing. convert -size 512x512 -depth 16 -define quantum:formatsigned gray:original.raw -auto-level result. I simply specify the data is signed using -define quantum-formatsigned.Then stretch the result to full dynamic range using -auto-level. There are times being stuck with a load of images that need to be cropped, resized or converted, but doing this by hand in an image editor is tedious work. Here is another way in ImageMagick that I think is more intuitive to your signed raw data. Creating Optimized GIFs in the Command-Line magick -size 60圆0 xc:none -fill white -stroke black \ -draw 'circle 30,30 5,20' circle.png magick circle.png -crop 10x10+40+3 +repage -scale 600 circlemag.png As you can see the edge of the circle on the left drawn (in PNG format) as a very clean looking (though slightly fuzzy) edge to the image.So, it may be a good idea to make all transparent pixels the same colour when saving PNG files, by using -alpha background.Įxample convert -size 512x512 xc:gray +noise random a.png # create an image of random 1 mark staff 1576107 6 Sep 11:37 a.png # 157kBĬonvert -size 512x512 xc:gray +noise random -alpha transparent a.png # recreate but make 1 mark staff 1793567 6 Sep 11:38 a.png # 179kB, extra transparency channelĬonvert -size 512x512 xc:gray +noise random -alpha transparent -alpha background a.png # make all transparent pixels 1 mark staff 1812 6 Sep 11:38 a.Image from New Old Stock Command-Line Image Processing with ImageMagick Table of Contents normally, the colour of transparent pixels is irrelevant because you can't see them, but uniform things generally compress better. rw-r-r- 1 mark staff 2361 5 Sep 21:04 rose64.pngĪnother way of optimising or reducing PNG filesizes is to use -strip to strip out any metadata from images - such as the date and time the picture was taken, the camera and lens model, the name of the program that created the image and the copyright and colour profiles.Īlso, worth bearing in mind. Now convert the rose to 64 colours and check the size - down to 2,361 bytes convert rose: -colors 64 rose64.png ![]() Now convert the rose to 255 colours and check the size - it is down to 3,691 bytes: convert rose: -colors 255 rose255.png Ls -l 1 mark staff 6975 5 Sep 20:57 rose.png You can try something similar in ImageMagick like this.įirst, using the built-in rose: image, check the number of colours in the image - it is 3,019: convert rose: -format %k info:Īnd make a PNG of it and check the size - it is 6,975 bytes convert rose: rose.png Pngquant effectively quantizes, or reduces the number of colours in an image till just before there is a discernible drop in quality.
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