openjpeg.cpp

这个刚才那个的源代码

#include <stdio.h>  // needed by jpeglib.h
#include <string.h>
#include <setjmp.h>
extern "C" {  // stupid JPEG library
  #include <jpeglib.h>
}
#include "Open.h"
#include "SimpleImage.h"


namespace corona {

  static const int JPEG_BUFFER_SIZE = 4096;


  void    JPEG_init_source(j_decompress_ptr cinfo);
  boolean JPEG_fill_input_buffer(j_decompress_ptr cinfo);
  void    JPEG_skip_input_data(j_decompress_ptr cinfo, long num_bytes);
  void    JPEG_term_source(j_decompress_ptr cinfo);
  void    JPEG_error_exit(j_common_ptr cinfo);
  void    JPEG_emit_message(j_common_ptr cinfo, int msg_level);


  struct InternalStruct {
    struct {
      jpeg_error_mgr mgr;
      jmp_buf setjmp_buffer;
    } error_mgr;

    File* file;
    byte buffer[JPEG_BUFFER_SIZE];
  };

  //////////////////////////////////////////////////////////////////////////////

  Image* OpenJPEG(File* file) {

    // set up internal information
    InternalStruct is;
    is.file = file;

    // initialize the source manager
    jpeg_source_mgr mgr;
    mgr.bytes_in_buffer = 0;
    mgr.next_input_byte = NULL;
    mgr.init_source       = JPEG_init_source;
    mgr.fill_input_buffer = JPEG_fill_input_buffer;
    mgr.skip_input_data   = JPEG_skip_input_data;
    mgr.resync_to_restart = jpeg_resync_to_restart;  // use default
    mgr.term_source       = JPEG_term_source;
    
    // initialize decompressor
    jpeg_decompress_struct cinfo;
    jpeg_create_decompress(&cinfo);
    cinfo.client_data = &is;

    cinfo.err = jpeg_std_error(&is.error_mgr.mgr);
    is.error_mgr.mgr.error_exit = JPEG_error_exit;

    SimpleImage* image = 0;
    
    if (setjmp(is.error_mgr.setjmp_buffer)) {
      delete image;
      jpeg_destroy_decompress(&cinfo);
      return 0;
    }

    cinfo.src = &mgr;
    jpeg_read_header(&cinfo, TRUE);
    jpeg_start_decompress(&cinfo);

    // do we support the number of color components?
    if (cinfo.output_components != 1 && cinfo.output_components != 3) {
      jpeg_finish_decompress(&cinfo);
      jpeg_destroy_decompress(&cinfo);
      return 0;
    }

    // make a one-row-high sample array that will go away when done with image
    int row_stride = cinfo.output_width * cinfo.output_components;
    JSAMPARRAY buffer = (*cinfo.mem->alloc_sarray)(
      (j_common_ptr)&cinfo,
      JPOOL_IMAGE,
      row_stride,
      1);

    // allocate image
    unsigned width  = cinfo.output_width;
    unsigned height = cinfo.output_height;
    byte* pixels = new byte[width * height * 3];
    memset(pixels, 0, width * height * 3);

    // create the image object now, so that if the error handler is called,
    // the longjmp code will know what to free
    image = new SimpleImage(width, height, PF_R8G8B8, pixels);

    // read the scanlines
    bool finished = true;
    while (cinfo.output_scanline < height) {
      int num_rows = jpeg_read_scanlines(&cinfo, buffer, 1);
      if (num_rows == 0) {
        finished = false;
        break;
      }

      // copy scanline into pixel buffer
      if (cinfo.output_components == 1) {        // greyscale
        byte* in = (byte*)(*buffer);
        for (unsigned i = 0; i < width * num_rows; ++i) {
          *pixels++ = *in; // red
          *pixels++ = *in; // green
          *pixels++ = *in; // blue
          ++in;
        }
      } else if (cinfo.output_components == 3) { // RGB
        memcpy(pixels, (*buffer), num_rows * width * 3);
        pixels += num_rows * width * 3;
      }
    }

    // finish up
    if (finished) {
      jpeg_finish_decompress(&cinfo);
    }
    jpeg_destroy_decompress(&cinfo);

    return image;
  }

  //////////////////////////////////////////////////////////////////////////////

  void JPEG_init_source(j_decompress_ptr cinfo) {
    // no initialization required
  }

  //////////////////////////////////////////////////////////////////////////////

  boolean JPEG_fill_input_buffer(j_decompress_ptr cinfo) {
    // more or less copied from jdatasrc.c

    InternalStruct* is = (InternalStruct*)(cinfo->client_data);

    int nbytes = is->file->read(is->buffer, JPEG_BUFFER_SIZE);
    if (nbytes <= 0) {
      /* Insert a fake EOI marker */
      is->buffer[0] = (JOCTET)0xFF;
      is->buffer[1] = (JOCTET)JPEG_EOI;
      nbytes = 2;
    }

    cinfo->src->bytes_in_buffer = nbytes;
    cinfo->src->next_input_byte = is->buffer;
    return TRUE;
  }

  //////////////////////////////////////////////////////////////////////////////

  void JPEG_skip_input_data(j_decompress_ptr cinfo, long num_bytes) {
    //InternalStruct* is = (InternalStruct*)(cinfo->client_data);
    if (num_bytes > 0) {
      while (num_bytes > (long)cinfo->src->bytes_in_buffer) {
        num_bytes -= (long)cinfo->src->bytes_in_buffer;
        JPEG_fill_input_buffer(cinfo);
      }
      cinfo->src->next_input_byte += (size_t)num_bytes;
      cinfo->src->bytes_in_buffer -= (size_t)num_bytes;
    }
  }

  //////////////////////////////////////////////////////////////////////////////

  void JPEG_term_source(j_decompress_ptr cinfo) {
    // nothing to do here...
  }

  //////////////////////////////////////////////////////////////////////////////

  void JPEG_error_exit(j_common_ptr cinfo) {
    InternalStruct* is = (InternalStruct*)(cinfo->client_data);
    longjmp(is->error_mgr.setjmp_buffer, 1);
  }

  //////////////////////////////////////////////////////////////////////////////

  void JPEG_emit_message(j_common_ptr /*cinfo*/, int /*msg_level*/) {
    // ignore error messages
  }

  //////////////////////////////////////////////////////////////////////////////

}