1 /*
   2  * Copyright (c) 1996, 2012, Oracle and/or its affiliates. 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.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 /*
  27  * This file implements some of the standard utility procedures used
  28  * by the image conversion package.
  29  */
  30 

  31 #include "img_globals.h"
  32 
  33 #include "java_awt_image_IndexColorModel.h"
  34 #include "java_awt_Transparency.h"
  35 
  36 /*
  37  * This function constructs an 8x8 ordered dither array which can be
  38  * used to dither data into an output range with discreet values that
  39  * differ by the value specified as quantum.  A monochrome screen would
  40  * use a dither array constructed with the quantum 256.
  41  * The array values produced are unsigned and intended to be used with
  42  * a lookup table which returns the next color darker than the error
  43  * adjusted color used as the index.
  44  */
  45 void
  46 make_uns_ordered_dither_array(uns_ordered_dither_array oda,
  47                               int quantum)
  48 {
  49     int i, j, k;
  50 
  51     oda[0][0] = 0;
  52     for (k = 1; k < 8; k *= 2) {
  53         for (i = 0; i < k; i++) {
  54             for (j = 0; j < k; j++) {
  55                 oda[ i ][ j ] = oda[i][j] * 4;
  56                 oda[i+k][j+k] = oda[i][j] + 1;
  57                 oda[ i ][j+k] = oda[i][j] + 2;
  58                 oda[i+k][ j ] = oda[i][j] + 3;
  59             }
  60         }
  61     }
  62     for (i = 0; i < 8; i++) {
  63         for (j = 0; j < 8; j++) {
  64             oda[i][j] = oda[i][j] * quantum / 64;
  65         }
  66     }
  67 }
  68 
  69 /*
  70  * This function constructs an 8x8 ordered dither array which can be
  71  * used to dither data into an output range with discreet values that
  72  * are distributed over the range from minerr to maxerr around a given
  73  * target color value.
  74  * The array values produced are signed and intended to be used with
  75  * a lookup table which returns the closest color to the error adjusted
  76  * color used as an index.
  77  */
  78 void
  79 make_sgn_ordered_dither_array(char* oda, int minerr, int maxerr)
  80 {
  81     int i, j, k;
  82 
  83     oda[0] = 0;
  84     for (k = 1; k < 8; k *= 2) {
  85         for (i = 0; i < k; i++) {
  86             for (j = 0; j < k; j++) {
  87                 oda[(i<<3) + j] = oda[(i<<3)+j] * 4;
  88                 oda[((i+k)<<3) + j+k] = oda[(i<<3)+j] + 1;
  89                 oda[(i<<3) + j+k] = oda[(i<<3)+j] + 2;
  90                 oda[((i+k)<<3) + j] = oda[(i<<3)+j] + 3;
  91             }
  92         }
  93     }
  94     k = 0;
  95     for (i = 0; i < 8; i++) {
  96         for (j = 0; j < 8; j++) {
  97             oda[k] = oda[k] * (maxerr - minerr) / 64 + minerr;
  98             k++;
  99         }
 100     }
 101 }
 102 
 103 #ifdef TESTING
 104 #include <stdio.h>
 105 
 106 /* Function to test the ordered dither error matrix initialization function. */
 107 main(int argc, char **argv)
 108 {
 109     int i, j;
 110     int quantum;
 111     int max, val;
 112     uns_ordered_dither_array oda;
 113 
 114     if (argc > 1) {
 115         quantum = atoi(argv[1]);
 116     } else {
 117         quantum = 64;
 118     }
 119     make_uns_ordered_dither_array(oda, quantum);
 120     for (i = 0; i < 8; i++) {
 121         for (j = 0; j < 8; j++) {
 122             val = oda[i][j];
 123             printf("%4d", val);
 124             if (max < val) {
 125                 max = val;
 126             }
 127         }
 128         printf("\n");
 129     }
 130     printf("\nmax = %d\n", max);
 131 }
 132 #endif /* TESTING */
--- EOF ---