Wireless Projector Adapter
Demonstration Software
 
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デモ用ソフト開発メモとか。

libjpegの使い方†

#include <stdio.h>
#include <stdlib.h>
#include <jpeglib.h>

int main(int argc, char *argv[]) {
  struct jpeg_decompress_struct cinfo;
  struct jpeg_error_mgr jerr;
  FILE *infile;
  FILE *outfile;
  char filename[BUFSIZ];
  int ***data;
  unsigned char *line_buf;
  int width, height, ncomp;
  int c, i, j;

  if (argc != 2) {
    printf("Usage: test infile\n");
    exit(1);
  }
  sprintf(filename, "%s", argv[1]);

  cinfo.err = jpeg_std_error(&jerr);
  jpeg_create_decompress(&cinfo);

  if ((infile = fopen(filename, "rb")) == NULL) {
    fprintf(stderr, "can't open %s\n", filename);
    exit(1);
  }
  jpeg_stdio_src(&cinfo, infile);

  jpeg_read_header(&cinfo, TRUE);
  
  jpeg_start_decompress(&cinfo); 

  width = cinfo.output_width;
  height = cinfo.output_height;
  ncomp = cinfo.out_color_components;
  printf("Width: %d\n", width);
  printf("Height: %d\n", height);
  printf("#comps: %d\n", ncomp);

  data = malloc(ncomp * sizeof(int **));
  for (c = 0; c < ncomp; ++c) {
    data[c] = malloc(height * sizeof(int *));
    for (j = 0; j < height; ++j)
      data[c][j] = malloc(width * sizeof(int));
  }

  line_buf = malloc(ncomp * width * sizeof(unsigned char));
  j = 0;
  while (jpeg_read_scanlines(&cinfo, &line_buf, 1)) {
   for (i = 0; i < width; ++i)
     for (c = 0; c < ncomp; ++c)
      data[c][j][i] = line_buf[ncomp * i + c];
   ++j;
  } 

  jpeg_finish_decompress(&cinfo);
  close(infile);
  jpeg_destroy_decompress(&cinfo);

  if ((outfile = fopen("hoge.ppm", "wb")) == NULL) {
    fprintf(stderr, "can't open %s\n", filename);
    exit(1);
  }

  fprintf(outfile, "P6\n# %s\n%d %d \n255\n", "ppm", width, height);
  for (j = 0; j < height; ++j)
    for (i = 0; i < width; ++i)
      for (c = 0; c < ncomp; ++c) 
	fputc(data[c][j][i], outfile);
  close(outfile); 
}
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