Convert IplImage into a JPEG without using CvSaveImage in OpenCV

Question

I wish to convert an IplImage into a JPEG image in the memory (in order to stream it as M-JPEG frame over sockets) . I know I can use CvSaveImage for this, that creates a jpeg file, I read it again and then stream it over the network. I wish to avoid this extra disk write-read ops for faster operation. Any insights ?

Answer 1

If your tag is correct and this is in C# then you should check out OpenCVSharp.

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

With it you can do...

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

I also found an example of someone doing it using VC++.NET

//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);
}

Good luck!

Answer 2

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

Answer 3

Check out this question. I am not sure how you can use the solution in C#, but maybe it can help.

Answer 4

Pretty Simple

All you need to load files from the memory buffer is a different src manager (libjpeg). I have tested the following code in Ubuntu 8.10.

/**************** 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; }

Then the usage is pretty simple. You may need to replace SIZEOF() with sizeof(). Find a standard decompression example. Just replace "jpeg_stdio_src" with "jpeg_memory_src". Hope that helps!