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comparison lcdtest/showppm.c @ 17:43cc53581975

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lcdtest: PPM image display implemented
author Mychaela Falconia <falcon@freecalypso.org>
date Sat, 07 Apr 2018 21:57:54 +0000
parents
children f3671d3ad953
comparison
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16:1e94c7d4af03 17:43cc53581975
1 #include <stdio.h>
2 #include <ctype.h>
3 #include <stdlib.h>
4
5 char *ppm_filename;
6 FILE *ppmfile;
7 int ppm_is_ascii; /* P3 format instead of P6 */
8
9 /*
10 * This function reads one ASCII-encoded integer from a PPM file.
11 * It handles the white space and comment rules of the PPM format.
12 */
13 static int
14 ppm_get_ascii_number()
15 {
16 int accum, c;
17
18 do {
19 c = getc(ppmfile);
20 if (c < 0) {
21 badeof: fprintf(stderr, "%s: unexpected EOF\n", ppm_filename);
22 return(-1);
23 }
24 if (c == '#') {
25 do
26 c = getc(ppmfile);
27 while (c >= 0 && c != '\n');
28 if (c != '\n')
29 goto badeof;
30 }
31 } while (isspace(c));
32 if (!isdigit(c)) {
33 fprintf(stderr,
34 "%s: unexpected data where a number was expected\n",
35 ppm_filename);
36 return(-1);
37 }
38 for (accum = c - '0'; ; ) {
39 c = getc(ppmfile);
40 if (c < 0 || isspace(c))
41 break;
42 if (!isdigit(c)) {
43 fprintf(stderr,
44 "%s: bad character in the middle of a number\n",
45 ppm_filename);
46 return(-1);
47 }
48 accum = accum * 10 + c - '0';
49 }
50 return accum;
51 }
52
53 /*
54 * This function reads and parses the PPM header of our input file.
55 */
56 static int
57 ppm_read_header()
58 {
59 int magic1, magic2;
60 int rd;
61
62 magic1 = getc(ppmfile);
63 magic2 = getc(ppmfile);
64 if (magic1 == 'P' && magic2 == '3')
65 ppm_is_ascii = 1;
66 else if (magic1 == 'P' && magic2 == '6')
67 ppm_is_ascii = 0;
68 else {
69 fprintf(stderr, "%s: P3 or P6 format expected\n", ppm_filename);
70 return(-1);
71 }
72 rd = ppm_get_ascii_number();
73 if (rd < 0)
74 return(-1);
75 if (rd != 176) {
76 fprintf(stderr, "%s: width is not 176\n", ppm_filename);
77 return(-1);
78 }
79 rd = ppm_get_ascii_number();
80 if (rd < 0)
81 return(-1);
82 if (rd != 220) {
83 fprintf(stderr, "%s: height is not 220\n", ppm_filename);
84 return(-1);
85 }
86 rd = ppm_get_ascii_number();
87 if (rd < 0)
88 return(-1);
89 if (rd != 255) {
90 fprintf(stderr, "%s: maxval is not 255\n", ppm_filename);
91 return(-1);
92 }
93 return(0);
94 }
95
96 /*
97 * This function reads a single R, G or B value from a PPM file.
98 */
99 static int
100 ppm_get_pixval()
101 {
102 int c;
103
104 if (ppm_is_ascii)
105 return ppm_get_ascii_number();
106 c = getc(ppmfile);
107 if (c < 0) {
108 fprintf(stderr, "%s: EOF while reading binary pixel data\n",
109 ppm_filename);
110 return(-1);
111 }
112 return c;
113 }
114
115 static int
116 ppm_get_rgb()
117 {
118 int r, g, b;
119
120 r = ppm_get_pixval();
121 if (r < 0)
122 return(-1);
123 g = ppm_get_pixval();
124 if (g < 0)
125 return(-1);
126 b = ppm_get_pixval();
127 if (b < 0)
128 return(-1);
129 /* convert to 5:6:5 */
130 r >>= 3;
131 g >>= 2;
132 b >>= 3;
133 return (r << 11) | (g << 5) | b;
134 }
135
136 cmd_show(argc, argv)
137 char **argv;
138 {
139 int rc;
140 unsigned n;
141
142 ppm_filename = argv[1];
143 ppmfile = fopen(ppm_filename, "r");
144 if (!ppmfile) {
145 perror(ppm_filename);
146 return(-1);
147 }
148 rc = ppm_read_header();
149 if (rc < 0) {
150 fclose(ppmfile);
151 return(-1);
152 }
153 write_ir(0x20);
154 write_dr(0);
155 write_ir(0x21);
156 write_dr(0);
157 write_ir(0x22);
158 for (n = 0; n < 176*220; n++) {
159 rc = ppm_get_rgb();
160 if (rc < 0) {
161 fclose(ppmfile);
162 return(-1);
163 }
164 write_dr(rc);
165 }
166 fclose(ppmfile);
167 return(0);
168 }