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 /* Table of CRCs of all 8-bit messages. */
  11 static unsigned long crc_table[256];
  12
  13 /* Flag: has the table been computed? Initially false. */
  14 static int crc_table_computed = 0;
  15
  16 /* Make the table for a fast CRC. */
  17 static void make_crc_table(void)
  18 {
  19         unsigned long c;
  20         int n, k;
  21
  22         for (n = 0; n < 256; n++) {
  23                 c = (unsigned long) n;
  24                 for (k = 0; k < 8; k++) {
  25                         if (c & 1)
  26                                 c = 0xedb88320L ^ (c >> 1);
  27                         else
  28                                 c = c >> 1;
  29                 }
  30                 crc_table[n] = c;
  31         }
  32         crc_table_computed = 1;
  33 }
  34
  35 /* Update a running CRC with the bytes buf[0..len-1]--the CRC
  36    should be initialized to all 1's, and the transmitted value
  37    is the 1's complement of the final running CRC (see the
  38    crc() routine below). */
  39
  40 static unsigned long update_crc(unsigned long crc, unsigned char *buf,
  41                 int len)
  42 {
  43         unsigned long c = crc;
  44         int n;
  45
  46         if (!crc_table_computed)
  47                 make_crc_table();
  48         for (n = 0; n < len; n++) {
  49                 c = crc_table[(c ^ buf[n]) & 0xff] ^ (c >> 8);
  50         }
  51         return c;
  52 }
  53
  54 /* Return the CRC of the bytes buf[0..len-1]. */
  55 static unsigned long crc(unsigned char *buf, int len)
  56 {
  57         return update_crc(0xffffffffL, buf, len) ^ 0xffffffffL;
  58 }
  59
  60 unsigned char *lcd2png(unsigned char *lcd, int *len)
  61 {
  62         unsigned char screen_conv[320*234*3];
  63         unsigned char lut[256][3];
  64         unsigned char *image;
  65         unsigned char *outpos;
  66         static const unsigned char png[] = {137, 80, 78, 71, 13, 10, 26, 10};
  67         static unsigned char ihdr[] = {'I', 'H', 'D', 'R',
  68                 0x00, 0x00, 0x01, 0x40, /* 320 - Width */
  69                 0x00, 0x00, 0x00, 0xea, /* 234 - Height */
  70                 0x08, /* Bit depth */
  71                 0x02, /* RGB Truecolor, Colour type */
  72                 0x00, /* Deflate, Compression method */
  73                 0x00, /* None, Filter method */
  74                 0x00  /* No interlace, Interlace method */
  75                 };
  76         static unsigned char idat[] = {'I', 'D', 'A', 'T'};
  77         static unsigned char iend[] = {'I', 'E', 'N', 'D'};
  78         uint32_t l;
  79         int i;
  80         int toalloc = 0;
  81         z_stream strm;
  82
  83         for(i = 0; i < 256; i++) {
  84                 lut[i][0] = ((i >> 6) * 0x55);
  85                 lut[i][1] = ((((i >> 3) & 7) * 0x49) >> 1);
  86                 lut[i][2] = (((i & 7) * 0x49) >> 1);
  87         }
  88
  89         for(i = 0; i < sizeof(screen_conv); i += 3) {
  90                 screen_conv[i] = lut[lcd[i/3]][0];
  91                 screen_conv[i+1] = lut[lcd[i/3]][1];
  92                 screen_conv[i+2] = lut[lcd[i/3]][2];
  93         }
  94
  95         strm.zalloc = Z_NULL;
  96         strm.zfree = Z_NULL;
  97         strm.opaque = Z_NULL;
  98         if (deflateInit(&strm, 9) != Z_OK) {
  99                 perror("deflateInit");
 100                 exit(EXIT_FAILURE);
 101         }
 102
 103
 104         image = malloc(320*234*2); /* TODO: FIXME! */
 105         outpos = image;
 106         memcpy(outpos, png, sizeof(png));
 107         outpos += sizeof(png);
 108
 109         l = htonl(sizeof(ihdr) - 4); /* "IHDR" is not counted */
 110         memcpy(outpos, &l, sizeof(l));
 111         outpos += sizeof(l);
 112         memcpy(outpos, ihdr, sizeof(ihdr));
 113         outpos += sizeof(ihdr);
 114         l = crc(ihdr, sizeof(ihdr));
 115         memcpy(outpos, &l, sizeof(l));
 116         outpos += sizeof(l);
 117
 118         l = htonl(sizeof(iend) - 4); /* "IEND" is not counted */
 119         memcpy(outpos, &l, sizeof(l));
 120         outpos += sizeof(l);
 121         memcpy(outpos, iend, sizeof(iend));
 122         outpos += sizeof(iend);
 123         l = crc(iend, sizeof(iend));
 124         memcpy(outpos, &l, sizeof(l));
 125         outpos += sizeof(l);
 126
 127         *len = (int)(outpos - image);
 128         return image;
 129 }