1 /* 2 PPImagePixelAlphaPremultiplyTables.h 3 4 Copyright 2013-2018 Josh Freeman 5 http://www.twilightedge.com 6 7 This file is part of PikoPixel for Mac OS X and GNUstep. 8 PikoPixel is a graphical application for drawing & editing pixel-art images. 9 10 PikoPixel is free software: you can redistribute it and/or modify it under 11 the terms of the GNU Affero General Public License as published by the 12 Free Software Foundation, either version 3 of the License, or (at your 13 option) any later version approved for PikoPixel by its copyright holder (or 14 an authorized proxy). 15 16 PikoPixel is distributed in the hope that it will be useful, but WITHOUT ANY 17 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS 18 FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more 19 details. 20 21 You should have received a copy of the GNU Affero General Public License 22 along with this program. If not, see <http://www.gnu.org/licenses/>. 23 */ 24 25 #import <Foundation/Foundation.h> 26 #import "PPBitmapPixelTypes.h" 27 28 // Lookup tables for premultiplying & unpremultiplying image bitmap pixels' color values with 29 // their alpha values. (Table lookups are faster than multiplying/dividing+rounding-off). 30 // 31 // Tables are stored as a global array - one lookup table for each possible alpha value [0-255]; 32 // Each lookup table contains entries for all possible color-channel values [0-255]. 33 // 34 // To premultiply an image pixel: 35 // 36 // premultiplyTable = gImageAlphaPremultiplyTables[imagePixel.alphaComponent] 37 // premultipliedImagePixel.redComponent = premultiplyTable[imagePixel.redComponent] 38 // premultipliedImagePixel.greenComponent = premultiplyTable[imagePixel.greenComponent] 39 // premultipliedImagePixel.blueComponent = premultiplyTable[imagePixel.blueComponent] 40 // 41 // (Same process for unpremultiplying) 42 43 44 extern PPImagePixelComponent *gImageAlphaPremultiplyTables[], 45 *gImageAlphaUnpremultiplyTables[]; 46 47 48 #define macroAlphaPremultiplyTableForImagePixel(imagePixel) \ 49 gImageAlphaPremultiplyTables[macroImagePixelComponent_Alpha(imagePixel)] 50 51 #define macroAlphaUnpremultiplyTableForImagePixel(imagePixel) \ 52 gImageAlphaUnpremultiplyTables[macroImagePixelComponent_Alpha(imagePixel)] 53