git.zerfleddert.de Git - rigol/blob - png.c

   1 #include <string.h>
   2 #include <stdint.h>
   3 #include <arpa/inet.h>
   4 #include <zlib.h>
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7
   8 #include "png.h"
   9
  10 #define CHUNK 16384
  11 #define WIDTH 320
  12 #define HEIGHT 234
  13
  14 /* Table of CRCs of all 8-bit messages. */
  15 static unsigned long crc_table[256];
  16
  17 /* Flag: has the table been computed? Initially false. */
  18 static int crc_table_computed = 0;
  19
  20 /* Make the table for a fast CRC. */
  21 static void make_crc_table(void)
  22 {
  23         unsigned long c;
  24         int n, k;
  25
  26         for (n = 0; n < 256; n++) {
  27                 c = (unsigned long) n;
  28                 for (k = 0; k < 8; k++) {
  29                         if (c & 1)
  30                                 c = 0xedb88320L ^ (c >> 1);
  31                         else
  32                                 c = c >> 1;
  33                 }
  34                 crc_table[n] = c;
  35         }
  36         crc_table_computed = 1;
  37 }
  38
  39 /* Update a running CRC with the bytes buf[0..len-1]--the CRC
  40    should be initialized to all 1's, and the transmitted value
  41    is the 1's complement of the final running CRC (see the
  42    crc() routine below). */
  43
  44 static unsigned long update_crc(unsigned long crc, unsigned char *buf,
  45                 int len)
  46 {
  47         unsigned long c = crc;
  48         int n;
  49
  50         if (!crc_table_computed)
  51                 make_crc_table();
  52         for (n = 0; n < len; n++) {
  53                 c = crc_table[(c ^ buf[n]) & 0xff] ^ (c >> 8);
  54         }
  55         return c;
  56 }
  57
  58 /* Return the CRC of the bytes buf[0..len-1]. */
  59 static unsigned long crc(unsigned char *buf, int len)
  60 {
  61         return update_crc(0xffffffffL, buf, len) ^ 0xffffffffL;
  62 }
  63
  64 unsigned char *lcd2png(unsigned char *lcd, int *len)
  65 {
  66         unsigned char screen_conv[(WIDTH*HEIGHT*3)+HEIGHT]; /* 320*234 RGB + scanline filter byte */
  67         unsigned char *pos;
  68         unsigned char lut[256][3];
  69         unsigned char *screen_deflated;
  70         int deflated_size;
  71         unsigned char *image = NULL;
  72         unsigned char *outpos;
  73         static const unsigned char png[] = {137, 80, 78, 71, 13, 10, 26, 10};
  74         static unsigned char idat[] = {'I', 'D', 'A', 'T'};
  75         static unsigned char iend[] = {'I', 'E', 'N', 'D'};
  76         static unsigned char ihdr[] = {'I', 'H', 'D', 'R',
  77                 0x00, 0x00, 0x01, 0x40, /* 320 - Width */
  78                 0x00, 0x00, 0x00, 0xea, /* 234 - Height */
  79                 0x08, /* Bit depth */
  80                 0x02, /* RGB Truecolor, Colour type */
  81                 0x00, /* Deflate, Compression method */
  82                 0x00, /* Adaptive, Filter method */
  83                 0x00  /* No interlace, Interlace method */
  84                 };
  85         uint32_t l;
  86         int i;
  87         int ret;
  88         int toalloc = 0;
  89         int flush;
  90         z_stream strm;
  91
  92         for(i = 0; i < 256; i++) {
  93                 lut[i][0] = ((i >> 6) * 0x55);
  94                 lut[i][1] = ((((i >> 3) & 7) * 0x49) >> 1);
  95                 lut[i][2] = (((i & 7) * 0x49) >> 1);
  96         }
  97
  98         pos = screen_conv;
  99         for(i = 0; i < (WIDTH*HEIGHT); i++) {
 100                 if ((i % WIDTH) == 0) {
 101                         *pos++ = 0x00; /* No adaptive filter */
 102                 }
 103                 *pos++ = lut[lcd[i]][0];
 104                 *pos++ = lut[lcd[i]][1];
 105                 *pos++ = lut[lcd[i]][2];
 106         }
 107
 108         strm.zalloc = Z_NULL;
 109         strm.zfree = Z_NULL;
 110         strm.opaque = Z_NULL;
 111         if (deflateInit(&strm, Z_BEST_COMPRESSION) != Z_OK) {
 112                 perror("deflateInit");
 113                 exit(EXIT_FAILURE);
 114         }
 115
 116         strm.avail_in = sizeof(screen_conv);
 117         strm.next_in = screen_conv;
 118
 119         toalloc = 0;
 120         strm.avail_out = 0;
 121         screen_deflated = NULL;
 122         flush = Z_NO_FLUSH;
 123
 124         do {
 125                 if (strm.avail_out == 0) {
 126                         toalloc += CHUNK;
 127                         screen_deflated = realloc(screen_deflated, toalloc);
 128                         if (screen_deflated == NULL) {
 129                                 perror("realloc");
 130                                 exit(EXIT_FAILURE);
 131                         }
 132
 133                         strm.avail_out = CHUNK;
 134                         strm.next_out = screen_deflated + (toalloc - CHUNK);
 135                 }
 136
 137                 ret = deflate(&strm, flush);
 138                 if (ret == Z_STREAM_ERROR) {
 139                         perror("deflate");
 140                         exit(EXIT_FAILURE);
 141                 }
 142
 143                 if(strm.avail_in == 0) {
 144                         flush = Z_FINISH;
 145                 }
 146         } while(ret != Z_STREAM_END);
 147         deflated_size = toalloc - strm.avail_out;
 148
 149         deflateEnd(&strm);
 150
 151         image = malloc(sizeof(png) +
 152                 sizeof(ihdr) + 8 + /* 8 = length, csum */
 153                 sizeof(idat) + deflated_size + 8 +
 154                 sizeof(iend) + 8);
 155
 156         if (image == NULL) {
 157                 perror("malloc");
 158         }
 159
 160         outpos = image;
 161
 162         /* PNG signature */
 163         memcpy(outpos, png, sizeof(png));
 164         outpos += sizeof(png);
 165
 166         /* IHDR */
 167         l = htonl(sizeof(ihdr) - 4); /* "IHDR" is not counted */
 168         memcpy(outpos, &l, sizeof(l));
 169         outpos += sizeof(l);
 170         memcpy(outpos, ihdr, sizeof(ihdr));
 171         outpos += sizeof(ihdr);
 172         l = htonl(crc(ihdr, sizeof(ihdr)));
 173         memcpy(outpos, &l, sizeof(l));
 174         outpos += sizeof(l);
 175
 176         /* IDAT */
 177         l = htonl(deflated_size);
 178         memcpy(outpos, &l, sizeof(l));
 179         outpos += sizeof(l);
 180         memcpy(outpos, idat, sizeof(idat));
 181         outpos += sizeof(idat);
 182         memcpy(outpos, screen_deflated, deflated_size);
 183         free(screen_deflated);
 184         outpos +=deflated_size;
 185         l = htonl(crc(outpos-deflated_size-sizeof(idat), deflated_size+sizeof(idat)));
 186         memcpy(outpos, &l, sizeof(l));
 187         outpos += sizeof(l);
 188
 189         /* IEND */
 190         l = htonl(sizeof(iend) - 4); /* "IEND" is not counted */
 191         memcpy(outpos, &l, sizeof(l));
 192         outpos += sizeof(l);
 193         memcpy(outpos, iend, sizeof(iend));
 194         outpos += sizeof(iend);
 195         l = htonl(crc(iend, sizeof(iend)));
 196         memcpy(outpos, &l, sizeof(l));
 197         outpos += sizeof(l);
 198
 199         *len = (int)(outpos - image);
 200         return image;
 201 }