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 */