在 OpenCV 中不使用 CvSaveImage 将 IplImage 转换为 JPEG

Posted 2023-03-16

【中文标题】在 OpenCV 中不使用 CvSaveImage 将 IplImage 转换为 JPEG

【英文标题】：Convert IplImage into a JPEG without using CvSaveImage in OpenCV

【发布时间】：2010-10-16 09:59:53

【问题描述】：

我希望将 IplImage 转换为内存中的 JPEG 图像（以便将其作为 M-JPEG 帧通过套接字传输）。 我知道我可以为此使用 CvSaveImage，它创建一个 jpeg 文件，我再次读取它，然后通过网络传输它。 我希望避免这种额外的磁盘读写操作以加快操作。有什么见解吗？

【问题讨论】：

这真的是一个 C# 问题吗？ OpenCV 是一个 C/C++ 库，不是吗？

【参考方案1】：

查看this question。我不确定如何在 C# 中使用该解决方案，但也许它可以提供帮助。

【参考方案2】：

如果你的标签是正确的，并且这是在 C# 中，那么你应该检查一下 OpenCVSharp。

http://code.google.com/p/opencvsharp/

有了它，你可以做...

IplImage ipl = new IplImage("foo.png", LoadMode.Color);
Bitmap bitmap = ipl.ToBitmap();

我还发现了一个使用 VC++.NET 的示例

//IplImage -> Bitmap
void Fill_Bitmap(Bitmap* bitmap, IplImage* image)
    int nl= image->height;
    int nc= image->width * image->nChannels;
    int step= image->widthStep;
    unsigned char* data=reinterpret_cast<unsigned char*>(image->imageData);
    for(int i=0; i<nl; i++)
        for(int j=0; j<nc; j+= image->nChannels)
            bitmap->SetPixel(j/3,i,Color::FromArgb(data[j],data[j+1],data[j+2]));
        
        data+= step;
    

;

Assume that in your main function:

void main()
    ...
    imRGB=cvCreateImage( cvSize(col,row), 8, 3 );
    Tbitmap=new Bitmap(col,row,PixelFormat::Format24bppRgb);
    ...
    Fill_Bitmap(Tbitmap,imRGB);

祝你好运！

【参考方案3】：

很简单

从内存缓冲区加载文件所需的只是一个不同的 src 管理器 (libjpeg)。我已经在 Ubuntu 8.10 中测试了以下代码。

/******************************** First define mem buffer function bodies **************/
/*
 * memsrc.c
 *
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains decompression data source routines for the case of
 * reading JPEG data from a memory buffer that is preloaded with the entire
 * JPEG file.  This would not seem especially useful at first sight, but
 * a number of people have asked for it.
 * This is really just a stripped-down version of jdatasrc.c.  Comparison
 * of this code with jdatasrc.c may be helpful in seeing how to make
 * custom source managers for other purposes.
 */

/* this is not a core library module, so it doesn't define JPEG_INTERNALS */
include "jinclude.h"
include "jpeglib.h"
include "jerror.h"


/* Expanded data source object for memory input */

typedef struct 
  struct jpeg_source_mgr pub;   /* public fields */

  JOCTET eoi_buffer[2];     /* a place to put a dummy EOI */
 my_source_mgr;

typedef my_source_mgr * my_src_ptr;


/*
 * Initialize source --- called by jpeg_read_header
 * before any data is actually read.
 */

METHODDEF(void)
init_source (j_decompress_ptr cinfo)

  /* No work, since jpeg_memory_src set up the buffer pointer and count.
   * Indeed, if we want to read multiple JPEG images from one buffer,
   * this *must* not do anything to the pointer.
   */



/*
 * Fill the input buffer --- called whenever buffer is emptied.
 *
 * In this application, this routine should never be called; if it is called,
 * the decompressor has overrun the end of the input buffer, implying we
 * supplied an incomplete or corrupt JPEG datastream.  A simple error exit
 * might be the most appropriate response.
 *
 * But what we choose to do in this code is to supply dummy EOI markers
 * in order to force the decompressor to finish processing and supply
 * some sort of output image, no matter how corrupted.
 */

METHODDEF(boolean)
fill_input_buffer (j_decompress_ptr cinfo)

  my_src_ptr src = (my_src_ptr) cinfo->src;

  WARNMS(cinfo, JWRN_JPEG_EOF);

  /* Create a fake EOI marker */
  src->eoi_buffer[0] = (JOCTET) 0xFF;
  src->eoi_buffer[1] = (JOCTET) JPEG_EOI;
  src->pub.next_input_byte = src->eoi_buffer;
  src->pub.bytes_in_buffer = 2;

  return TRUE;



/*
 * Skip data --- used to skip over a potentially large amount of
 * uninteresting data (such as an APPn marker).
 *
 * If we overrun the end of the buffer, we let fill_input_buffer deal with
 * it.  An extremely large skip could cause some time-wasting here, but
 * it really isn't supposed to happen ... and the decompressor will never
 * skip more than 64K anyway.
 */

METHODDEF(void)
skip_input_data (j_decompress_ptr cinfo, long num_bytes)

  my_src_ptr src = (my_src_ptr) cinfo->src;

  if (num_bytes > 0) 
    while (num_bytes > (long) src->pub.bytes_in_buffer) 
      num_bytes -= (long) src->pub.bytes_in_buffer;
      (void) fill_input_buffer(cinfo);
      /* note we assume that fill_input_buffer will never return FALSE,
       * so suspension need not be handled.
       */
    
    src->pub.next_input_byte += (size_t) num_bytes;
    src->pub.bytes_in_buffer -= (size_t) num_bytes;
  



/*
 * An additional method that can be provided by data source modules is the
 * resync_to_restart method for error recovery in the presence of RST markers.
 * For the moment, this source module just uses the default resync method
 * provided by the JPEG library.  That method assumes that no backtracking
 * is possible.
 */


/*
 * Terminate source --- called by jpeg_finish_decompress
 * after all data has been read.  Often a no-op.
 *
 * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
 * application must deal with any cleanup that should happen even
 * for error exit.
 */

METHODDEF(void)
term_source (j_decompress_ptr cinfo)

  /* no work necessary here */



/*
 * Prepare for input from a memory buffer.
 */

GLOBAL(void)
jpeg_memory_src (j_decompress_ptr cinfo, const JOCTET * buffer, size_t bufsize)

  my_src_ptr src;

  /* The source object is made permanent so that a series of JPEG images
   * can be read from a single buffer by calling jpeg_memory_src
   * only before the first one.
   * This makes it unsafe to use this manager and a different source
   * manager serially with the same JPEG object.  Caveat programmer.
   */
  if (cinfo->src == NULL)  /* first time for this JPEG object? */
    cinfo->src = (struct jpeg_source_mgr *)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
                  SIZEOF(my_source_mgr));
  

  src = (my_src_ptr) cinfo->src;
  src->pub.init_source = init_source;
  src->pub.fill_input_buffer = fill_input_buffer;
  src->pub.skip_input_data = skip_input_data;
  src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
  src->pub.term_source = term_source;

  src->pub.next_input_byte = buffer;
  src->pub.bytes_in_buffer = bufsize;

那么用法就很简单了。您可能需要将 SIZEOF() 替换为 sizeof()。找一个标准的解压例子。只需将“jpeg_stdio_src”替换为“jpeg_memory_src”即可。希望对您有所帮助！

【参考方案4】：

使用 CxImage http://www.codeproject.com/KB/graphics/cximage.aspx