/* jpegtopdf: Assemble a bunch of JPEG files into a PDF file.
Syntax: jpegtopdf file-names
A bunch of JPEG files is taken as input and a PDF-1.1 file is printed to the standard output.
Requires jpeglib.
Compile with cc -ljpeg jpegtopdf.c -o jpegtopdf
For gcc you might need to use an addtional option -std=c99.
Written and copyrighted by Dmitri Pavlov in 2009.
Distributed under the terms of GNU General Public License version 3.
Feedback welcome via SMTP: host math.berkeley.edu, user pavlov. */

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

int offset = 0;

void print(const char *format, ...) {
  va_list ap;
  va_start(ap, format);
  int n = vprintf(format, ap);
  if (n < 0) {
    perror("vprintf");
    exit(1);
  }
  offset += n;
  va_end(ap);
}

int main(int argc, char *argv[]) {
  int *obj = malloc(sizeof(int) * 3 * argc);
  if (obj == 0) {
    perror("malloc");
    exit(1);
  }
  print("%%PDF-1.1\n%%\200\200\200\200\n");
  obj[1] = offset;
  print("1 0 obj << /Type /Catalog /Pages 2 0 R >> endobj\n");
  obj[2] = offset;
  print("2 0 obj << /Type /Pages /Count %d /Kids [", argc - 1);
  for (int k = 1; k < argc; k++)
    print(" %d 0 R", 3 * k);
  print(" ] >> endobj\n");
  for (int k = 1; k < argc; k++) {
    FILE *stream = fopen(argv[k], "rb");
    if (stream == 0) {
      perror("fopen");
      exit(1);
    }
    struct jpeg_decompress_struct cinfo;
    struct jpeg_error_mgr jerr;
    cinfo.err = jpeg_std_error(&jerr);
    jpeg_create_decompress(&cinfo);
    jpeg_stdio_src(&cinfo, stream);
    jpeg_read_header(&cinfo, TRUE);
    if (cinfo.density_unit == 0) {
      fprintf(stderr, "%s: unknown resolution, assuming 300\n", argv[k]);
      cinfo.density_unit = 1;
      cinfo.X_density = cinfo.Y_density = 300;
    }
    const char *cspace;
    if (cinfo.jpeg_color_space == JCS_RGB)
      cspace = "DeviceRGB";
    else if (cinfo.jpeg_color_space == JCS_GRAYSCALE)
      cspace = "DeviceGray";
    else if (cinfo.jpeg_color_space == JCS_YCbCr)
      cspace = "DeviceRGB";
    else {
      fprintf(stderr, "unknown color space %d\n", cinfo.jpeg_color_space);
      return 1;
    }
    int w = cinfo.image_width, h = cinfo.image_height;
    double sf = cinfo.density_unit == 1 ? 72 : 72 / 2.54;
    double ww = w * sf / cinfo.X_density, hh = h * sf / cinfo.Y_density;
    jpeg_destroy_decompress(&cinfo);
    if (fseek(stream, 0, SEEK_END) != 0) {
      perror("fseek");
      exit(1);
    }
    long size = ftell(stream);
    if (size == -1) {
      perror("ftell");
      exit(1);
    }
    if (fseek(stream, 0, SEEK_SET) != 0) {
      perror("fseek");
      exit(1);
    }
    obj[3 * k] = offset;
    print("%d 0 obj << /Type /Page /Parent 2 0 R /Resources << /ProcSet [ /PDF /ImageB ] "
          "/XObject << /image %d 0 R >> >> /MediaBox [ 0 0 %.2f %.2f ] "
          "/Contents [ %d 0 R ] >> endobj\n",
          3 * k, 3 * k + 2, ww, hh, 3 * k + 1);
    obj[3 * k + 1] = offset;
    char s[64];
    sprintf(s, "%.2f 0 0 %.2f 0 0 cm /image Do", ww, hh);
    print("%d 0 obj << /Length %d >> stream\n%s\nendstream endobj\n", 3 * k + 1, strlen(s), s);
    obj[3 * k + 2] = offset;
    print("%d 0 obj << /Length %d /Filter /DCTDecode /Subtype /Image /Width %d /Height %d "
          "/ColorSpace /%s /BitsPerComponent 8 >> stream\n",
          3 * k + 2, size, w, h, cspace);
    int c;
    while ((c = fgetc(stream)) != EOF) {
      if (putchar(c) == EOF) {
        perror("putchar");
        exit(1);
      }
      offset++;
    }
    if (ferror(stream) != 0) {
      perror("fgetc");
      exit(1);
    }
    if (fclose(stream) != 0) {
      perror("fclose");
      exit(1);
    }
    print("\nendstream endobj\n");
  }
  int xref = offset;
  print("xref\n0 %d\n0000000000 65535 f \n", 3 * argc);
  for (int k = 1; k < 3 * argc; k++)
    print("%010d 00000 n \n", obj[k]);
  print("trailer << /Size %d /Root 1 0 R >>\nstartxref\n%d\n%%%%EOF\n", 3 * argc, xref);
  return 0;
}