Bilinear Resample Algorithm

 

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This is a true bilinear resampling algorithm. Because it's purly done in Lingo it's rather slow compared to resampling done by Xtras. The benefit is it's free.

-- Bilinear Image Resampling Code -- ©2005 by Josh Chunick (josh@chunick.com) -- code optimizations by Thomas Mavrofides -- This code is free to use in commercial applications -- or however you want.If you use this code you -- must keep the comments, including this message, -- intact. Feel free to add any changes or make improvements. -- -- inspired by VB code from vbAccelerator.com on bilinearResample2 (theImage, newWidth, newHeight, sharpen, amount)   --theImage = anImage.duplicate()   newImage = image(newWidth, newHeight, 32)   oldWidth = theImage.width - 1   oldHeight = theImage.height - 1      -- return the original image if the scale factor is 1   if newImage.rect = theImage.rect then return theImage      -- the look-up table for the original image (done for speed purposes)   -- this shaves off 600 milliseconds from my 320x240 test image   listX = []   listY = []   repeat with x = 0 to oldWidth     repeat with y = 0 to oldHeight       listY.add(theImage.getPixel(x,y))     end repeat     listX.add(listY)     listY = []   end repeat      -- get the ratio between the old image and the new one   xScale = (oldWidth) / float(newWidth)   yScale = (oldHeight) / float(newHeight)      -- draw each pixel in the new image   repeat with y = 1 to newHeight          -- generate the y calculation variables     dstY = (y - 1) * yScale     interplY = bitXor(dstY, 0)     calcY = dstY - interplY          repeat with x = 1 to newWidth       -- generate the x calculation variables       dstX = (x - 1) * xScale       interplX = bitXor(dstX, 0)       calcX = dstX - interplX              -- get the 4 pixels around the interpolated one       theColour1 = listX[interplX + 1][interplY + 1]       theColour2 = listX[interplX + 2][interplY + 1]       theColour3 = listX[interplX + 1][interplY + 2]       theColour4 = listX[interplX + 2][interplY + 2]              -- calculate the new colour       newColor1 = theColour1 * (1 - calcY) + theColour3 * calcY       newColor2 = theColour2 * (1 - calcY) + theColour4 * calcY       newColor= newColor1 * (1 - calcX) + newColor2 * calcX              --Set this pixel into the new image              newImage.setPixel(point(x - 1,y - 1), newColor)            end repeat   end repeat      return newImage    end