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Article contents:== chicken-stb-image [[toc:]] This is a [[http://call-cc.org|CHICKEN]] egg that wraps [[https://github.com/nothings/stb|stb_image.h]] version 2.19 from Sean Barrett and friends. It works on [[http://call-cc.org|CHICKEN]] 4 and 5. == API [[toc:]] <procedure>(read-image #!key channels)</procedure> <procedure>(load-image u8vector #!key channels)</procedure> Decodes an image into raw pixel data. {{read-image}} reads the image from from {{(current-input-port)}} while {{load-image}} gets this from the provided u8vector. The image type is detected by content, and may be: JPEG, PNG, TGA, BMP, PSD, GIF, HDR, PIC, PNM as explained in the heading comments of {{stb_image.h}}. Both procedures return 4 values: # raw pixel data (as u8vector) # width # height # number of channels You can force the number of channels with the {{channels}} keyword. If {{channels}} is {{#f}} or not given, the number of channels in the original image will be used. The size of the pixel data blob is always {{(* width height channels)}} bytes. The first pixel is the top-left-most in the image. Each pixel is {{channel}} number of bytes long. The number of channels define the pixel color, interleaved as follows: # grey # grey, alpha # red, green, blue # red, green, blue, alpha {{read-image}} may read beyond the image data, so the data in {{current-input-port}} should contain only one image. <procedure>(read-image-info)</procedure> <procedure>(load-image-info blob)</procedure> Like {{read-image}} and {{load-image}}, but does not load pixel data and should be faster. Returns three values: # width # height # number of channels Note that on 32-bit systems, blobs cannot be larger than 16M. This limits image sizes as pixel data is stored as blobs. === Examples For quick testing, you can read PNGs from ImageMagick's {{convert}}: $ convert -size 4x4 xc:blue -draw 'line 0,0 4,4' png:- | csi -R stb-image -p '(read-image)' #u8(0 0 0 0 0 234 0 0 255 0 0 255 0 0 234 0 0 0 0 0 234 0 0 255 0 0 255 0 0 234 0 0 0 0 0 234 0 0 255 0 0 255 0 0 234 0 0 0) 4 4 3 Which reveal the black line along the diagonal and informs that the image is 4x4 with 3-channels. Remerber to open files in {{#:binary}} mode for things to work on Windows: (with-input-from-file "rose.png" read-image-info #:binary) === Known limitations ===== backwards seek not implemented Some special-case images try to seek backwards in the internal API. This hasn't been implemented due to increased complexity: you may see a "backwards seek not implemented" error. If this is a show-stopper, contact the author. Description of your changes:

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