I have posted a demo stack in the forums:
https://forums.livecode.com/viewtopic.php?f=10&t=29935
Have a nice weekend!
Al
On Sat, Oct 7, 2017 at 1:52 AM, Alejandro Tejada <capellan2...@gmail.com>
wrote:
> Hi All,
>
> I am stuck trying to make this code for Bill Atkinson
> dithering algorithm much more faster.
> Any ways to speed this code?
> Follow the recipe and watch out for lines broken
> by mail character length limit.
>
> Recipe:
>
> 1) Import an small image (200x200 pixels) and
> name it as "Image" (you could import a small
> transparent png or a small jpg image)
>
> 2) Optionally, create a scrollbar type slider
> with a range between 0 and 255.
> Set the name of this scrollbar as "ThresholdDither"
> and move the slider to 127 or 0 or 255.
>
> 3) Paste the following script in a button and
> click on it to run this code:
>
> on mouseUp
>
> put the millisecs into startTime
> set the cursor to busy
>
> put the alphadata of img "Image" into tAlphaData
> put the imagedata of img "Image" into tVar
> -- img "Image" could be a grayscale image
> -- where all 3 channels: Red, Green, Blue
> -- are identical or a color image where only
> -- the red channel is used
>
> delete char 1 of tVar
> -- the first char of the imagedata is part
> -- of the alphadata or maskdata
> repeat with i = 1 to length(tVar) step 4
> put chartonum(char i of tVar) & space after fldhex
> end repeat
> delete last char of fldhex -- a space
> -- fldhex now contains a single channel of the RGB image
> -- converted to numbers between 0 and 255
>
> put the number of words of fldhex into lenghtofldhex
> put the width of img "Image" into tImageWidth
> put the height of img "Image" into tImageHeight
>
> repeat with i = 1 to lenghtofldhex step tImageWidth
> -- We need as many words per line, as pixels contains
> -- the image width (because each pixel is represented
> -- by a word and this word is number between 0 and 255)
>
> put word i to ( i + ((tImageWidth) - 1)) of fldhex & cr after fldhexa2
> end repeat
>
> put empty into fldhex
> delete last char of fldhexa2
> -- deleting the last cr character
>
> put the number of lines of fldhexa2 into sYsize
> put the number of words of line 1 of fldhexa2 into sXsize
>
> // get the scrollbar value
> -- tThreshold is a value between 0 and 255
> if existence(sb the "ThresholdDither") then
> put thumbPos of sb the "ThresholdDither" into tThreshold
> else
> put 127 into tThreshold
> end if
>
> repeat with tY = 1 to sYsize
> repeat with tX = 1 to sXsize
>
> put tX into tPixelPosition
>
> put word (tPixelPosition) of line tY of fldhexa2 into
> tOldPixelValue
>
> if round(tOldPixelValue) <= tThreshold then
> put 0 into tNewPixelValue
> else
> put 255 into tNewPixelValue
> end if
>
> put (tOldPixelValue - tNewPixelValue)/8 into tDifusionError
>
> -- Atkinson dither add the diffusion error
> -- to 6 adjacent pixels
> -- x o o
> -- o o o
> -- o
>
> put tNewPixelValue & space after fldhexa3
>
>
> if tPixelPosition < sXsize then
> put tDifusionError + word (tPixelPosition + 1) of line tY
> of fldhexa2 into word (tPixelPosition + 1) of line tY of fldhexa2
>
>
> if tPixelPosition < (sXsize-1) then
> put tDifusionError + word (tPixelPosition + 2) of line
> tY of fldhexa2 into word (tPixelPosition + 2) of line tY of fldhexa2
> end if
>
>
> end if
>
>
> if tY < sYsize then
>
>
> if tPixelPosition > 1 then
> put tDifusionError + word (tPixelPosition - 1) of line
> tY + 1 of fldhexa2 into word (tPixelPosition - 1) of line tY + 1 of fldhexa2
> end if
>
>
> put tDifusionError + word (tPixelPosition) of line tY + 1
> of fldhexa2 into word (tPixelPosition) of line tY + 1 of fldhexa2
>
>
> if tPixelPosition < sXsize then
> put tDifusionError + word (tPixelPosition + 1) of line
> tY + 1 of fldhexa2 into word (tPixelPosition + 1) of line tY + 1 of fldhexa2
> end if
>
>
> if tY < (sYsize - 1) then
> put tDifusionError + word (tPixelPosition) of line tY +
> 2 of fldhexa2 into word (tPixelPosition) of line tY + 2 of fldhexa2
> end if
>
>
> end if
>
> end repeat
> end repeat
>
> replace "0" with "00" in fldhexa3
> replace "255" with "FF" in fldhexa3
>
> repeat with i = 1 to the number of words of fldhexa3
> put 00 & word i of fldhexa3 & word i of fldhexa3 & word i of
> fldhexa3 after tVar2
> end repeat
> put binaryEncode("H*",tVar2) into tVar3
>
> create img
> set the height of it to the height of img "Image"
> set the width of it to the width of img "Image"
> set the imagedata of it to tVar3
> set the alphaData of it to tAlphaData
>
> put the millisecs - startTime && "milliseconds to create Atkinson
> Dither"
>
> end mouseUp
>
> Thanks in advance!
> Al
>
>
>
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