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- \l png.k
- / [[https://github.com/mthom/scryer-prolog/tree/master/logo]]
- png:1:fn:"scryer.png"
- $[~png.ispng[png];`err"Not a png file: ", fn;]
- (w;h):*png.ihdr@png
- idat:[email protected]@png
- data:png.unfilt[8](h,0N)#idat
- / mark each pixel as either bg color or not
- / extend each row to have length a multiple of 8
- bw:((0x5757d3d3dede~/:-2_'0N 8#)'data),\:0
- / collect this data as bytes
- / add a byte to the front to indicate no filtering
- bwdata:,/(`c$0),/:(`c$2/+0N 8#)'bw
- / build up a b/w png
- png0:png.PNGHDR
- / same dimensions, but now bit-depth 1, color-type 0
- png0,:png.mkchnk["IHDR";`c$,/((4#256)\'w,h),1 0 0 0 0]
- / "compress" at level 0
- png0,:png.mkchnk["IDAT";png.nocmp@bwdata]
- png0,:png.mkchnk["IEND";!0]
- "/tmp/bw.png" 1:png0
- / bottom image
- / [[https://www.w3.org/Graphics/PNG/Inline-img.html]]
- png:1:fn:"test.png"
- $[~png.ispng[png];`err"Not a png file: ",fn;]
- (w;h):*png.ihdr@png
- idat:[email protected]@png
- / Pull out the interlaced images
- c:png.iszs[w;h]
- PIXELWIDTH:3
- ii:(-1_+\0,(*|c)+PIXELWIDTH**/c)_idat
- / Unfilter each separately
- rr:png.unfilt[PIXELWIDTH]'((*|c),\:0N)#'ii
- / interlace back into a single image with no filtering
- dd:,/(`c$0),/:,/'(0N,w)#((0N,PIXELWIDTH)#,/,/'rr)@<<,/w#'h#png.A7
- png0:png.PNGHDR
- png0,:png.mkchnk["IHDR";`c$,/((4#256)\'w,h),8 2 0 0 0]
- png0,:png.mkchnk["IDAT";png.cmp@dd]
- png0,:png.mkchnk["IEND";!0]
- "/tmp/testing.png" 1:png0
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