| J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1996 Sun Microsystems, Inc. All Rights Reserved. |
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 | * |
| 5 | * This code is free software; you can redistribute it and/or modify it |
| 6 | * under the terms of the GNU General Public License version 2 only, as |
| 7 | * published by the Free Software Foundation. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun in the LICENSE file that accompanied this code. |
| 10 | * |
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 14 | * version 2 for more details (a copy is included in the LICENSE file that |
| 15 | * accompanied this code). |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License version |
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 20 | * |
| 21 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | /* |
| 27 | * This file contains macro definitions for the Encoding category of |
| 28 | * the macros used by the generic scaleloop function. |
| 29 | * |
| 30 | * This implementation uses an ordered dithering error matrix to |
| 31 | * produce a moderately high quality version of an image with only |
| 32 | * an 8-bit (or less) RGB colormap. The ordered dithering technique |
| 33 | * does not rely on the order in which the pixels are processed so |
| 34 | * this file can be used in cases where the ImageProducer has not |
| 35 | * specified the TopDownLeftRight delivery hint. The ordered dither |
| 36 | * technique is also much faster than the Floyd-Steinberg error diffusion |
| 37 | * algorithm so this implementation would also be appropriate for |
| 38 | * cases where performance is critical such as the processing of a |
| 39 | * video stream. |
| 40 | * |
| 41 | * This file can be used to provide the default implementation of the |
| 42 | * Encoding macros for RGB colormapped displays. |
| 43 | */ |
| 44 | |
| 45 | /* |
| 46 | * These definitions vector the standard macro names to the "Color" |
| 47 | * versions of those macros only if the "DitherDeclared" keyword has |
| 48 | * not yet been defined elsewhere. The "DitherDeclared" keyword is |
| 49 | * also defined here to claim ownership of the primary implementation |
| 50 | * even though this file does not rely on the definitions in any other |
| 51 | * files. |
| 52 | */ |
| 53 | #ifndef DitherDeclared |
| 54 | #define DitherDeclared |
| 55 | #define DeclareDitherVars DeclareAllColorDitherVars |
| 56 | #define InitDither InitColorDither |
| 57 | #define StartDitherLine StartColorDitherLine |
| 58 | #define DitherPixel ColorDitherPixel |
| 59 | #define DitherBufComplete ColorDitherBufComplete |
| 60 | #endif |
| 61 | |
| 62 | #define DeclareAllColorDitherVars \ |
| 63 | DeclareColorDitherVars \ |
| 64 | int relx, rely; |
| 65 | |
| 66 | #define DeclareColorDitherVars \ |
| 67 | extern uns_ordered_dither_array img_oda_red; \ |
| 68 | extern uns_ordered_dither_array img_oda_green; \ |
| 69 | extern uns_ordered_dither_array img_oda_blue; |
| 70 | |
| 71 | #define InitColorDither(cvdata, clrdata, dstTW) \ |
| 72 | do {} while (0) |
| 73 | |
| 74 | #define StartColorDitherLine(cvdata, dstX1, dstY) \ |
| 75 | do { \ |
| 76 | relx = dstX1 & 7; \ |
| 77 | rely = dstY & 7; \ |
| 78 | } while (0) |
| 79 | |
| 80 | /* |
| 81 | * The adjustments below are gross, but they are required due to |
| 82 | * the way color lookups are done. |
| 83 | * The second set of adjustments simply clips the values generated |
| 84 | * by the ordered dithering values to a limit of 256 which represents |
| 85 | * full intensity. |
| 86 | * The first set of adjustments prepares for the fact that when |
| 87 | * the final lookup is done, maximum intensity is represented by |
| 88 | * the value 256, but the input values go from 0 to 255. As a |
| 89 | * result, the maximum input intensity needs to be mapped from |
| 90 | * 255 to 256. The Floyd-Steinberg lookups use a rounding |
| 91 | * calculation to handle mapping the values near 255 to the maximum |
| 92 | * intensity, but ordered dithering uses a truncating calculation |
| 93 | * so the value 255 will be rounded down to the second highest |
| 94 | * intensity thereby causing an occasionaly dark pixel when rendering |
| 95 | * the maximum input intensity. Other intensities (less than 255) |
| 96 | * are left alone since modifying them would slightly disturb their |
| 97 | * error distribution. In particular, for red, the value 0xe0 has |
| 98 | * a maximum error of 0x1f added to it which must not be mapped to |
| 99 | * the maximum intensity since intensity 0xe0 can be represented |
| 100 | * exactly. So, a calculated 0xff (0xe0 + 0x1f) needs to be left |
| 101 | * less than 256, but a natural 255, or a calculated (>=) 256 |
| 102 | * should be mapped to maximum intensity. |
| 103 | */ |
| 104 | #define ColorDitherPixel(dstX, dstY, pixel, red, green, blue) \ |
| 105 | do { \ |
| 106 | if (red == 255) { \ |
| 107 | red = 256; \ |
| 108 | } else { \ |
| 109 | red += img_oda_red[relx][rely]; \ |
| 110 | if (red > 255) red = 256; \ |
| 111 | } \ |
| 112 | if (green == 255) { \ |
| 113 | green = 256; \ |
| 114 | } else { \ |
| 115 | green += img_oda_green[relx][rely]; \ |
| 116 | if (green > 255) green = 256; \ |
| 117 | } \ |
| 118 | if (blue == 255) { \ |
| 119 | blue = 256; \ |
| 120 | } else { \ |
| 121 | blue += img_oda_blue[relx][rely]; \ |
| 122 | if (blue > 255) blue = 256; \ |
| 123 | } \ |
| 124 | pixel = ColorCubeOrdMapUns(red, green, blue); \ |
| 125 | relx = (relx + 1) & 7; \ |
| 126 | } while (0) |
| 127 | |
| 128 | #define ColorDitherBufComplete(cvdata, dstX1) \ |
| 129 | do {} while (0) |