最近项目需要，学习学习OpenCV库。由于需要处理的图片较大，对其进行缩放时，总是出错。师弟说是由于OpenCV不能加载尺寸超过10000像素的图片。于是在OpenCV中文站查到，OpenCV在highgui的image.cpp文件中定义了下面这个max_img_size：

/*const unsigned max_img_size = 10000;*/ 注释掉
if( (bpp != 8 && bpp != 24 && bpp != 32) ||
        /*(unsigned)w >=  max_img_size || (unsigned)h >= max_img_size ||*/ 注释掉
        (origin != IPL_ORIGIN_TL && origin != IPL_ORIGIN_BL))
    {
        assert(0); // most probably, it is a programming error
        return false;
    }
...

        注释掉之后，重新编译highgui。现在能打开10000多点的了，但是还是有问题，调试定位到cxcore的cxarray.cpp中的cvCreateImage函数中：

// create IplImage header and allocate underlying data
CV_IMPL IplImage *
cvCreateImage( CvSize size, int depth, int channels )
{
    IplImage *img = 0;

    CV_FUNCNAME( "cvCreateImage" );

    __BEGIN__;

    CV_CALL( img = cvCreateImageHeader( size, depth, channels ));
    assert( img );
    CV_CALL( cvCreateData( img ));        // 报错

    __END__;

    if( cvGetErrStatus() < 0 )
        cvReleaseImage( &img );

    return img;
}

再进去：

// Allocates underlying array data
CV_IMPL void
cvCreateData( CvArr* arr )
{
    CV_FUNCNAME( "cvCreateData" );
    
    __BEGIN__;

    if( CV_IS_MAT_HDR( arr ))
    {
        size_t step, total_size;
        CvMat* mat = (CvMat*)arr;
        step = mat->step;

        if( mat->data.ptr != 0 )
            CV_ERROR( CV_StsError, "Data is already allocated" );

        if( step == 0 )
            step = CV_ELEM_SIZE(mat->type)*mat->cols;

        total_size = step*mat->rows + sizeof(int) + CV_MALLOC_ALIGN;
        CV_CALL( mat->refcount = (int*)cvAlloc( (size_t)total_size ));
        mat->data.ptr = (uchar*)cvAlignPtr( mat->refcount + 1, CV_MALLOC_ALIGN );
        *mat->refcount = 1;
    }
    else if( CV_IS_IMAGE_HDR(arr))
    {
        IplImage* img = (IplImage*)arr;

        if( img->imageData != 0 )
            CV_ERROR( CV_StsError, "Data is already allocated" );

        if( !CvIPL.allocateData )
        {
            CV_CALL( img->imageData = img->imageDataOrigin = 
                        (char*)cvAlloc( (size_t)img->imageSize ));        // 报错
        }
        else
        {
            int depth = img->depth;
            int width = img->width;

            if( img->depth == IPL_DEPTH_32F || img->nChannels == 64 )
            {
                img->width *= img->depth == IPL_DEPTH_32F ? sizeof(float) : sizeof(double);
                img->depth = IPL_DEPTH_8U;
            }

            CvIPL.allocateData( img, 0, 0 );

            img->width = width;
            img->depth = depth;
        }
    }
    else if( CV_IS_MATND_HDR( arr ))
    {
        CvMatND* mat = (CvMatND*)arr;
        int i;
        size_t total_size = CV_ELEM_SIZE(mat->type);

        if( mat->data.ptr != 0 )
            CV_ERROR( CV_StsError, "Data is already allocated" );

        if( CV_IS_MAT_CONT( mat->type ))
        {
            total_size = (size_t)mat->dim[0].size*(mat->dim[0].step != 0 ?
                         mat->dim[0].step : total_size);
        }
        else
        {
            for( i = mat->dims - 1; i >= 0; i-- )
            {
                size_t size = (size_t)mat->dim[i].step*mat->dim[i].size;

                if( total_size < size )
                    total_size = size;
            }
        }
        
        CV_CALL( mat->refcount = (int*)cvAlloc( total_size +
                                        sizeof(int) + CV_MALLOC_ALIGN ));
        mat->data.ptr = (uchar*)cvAlignPtr( mat->refcount + 1, CV_MALLOC_ALIGN );
        *mat->refcount = 1;
    }
    else
    {
        CV_ERROR( CV_StsBadArg, "unrecognized or unsupported array type" );
    }

    __END__;
}

下面是cxalloc.cpp中的cvAlloc：

CV_IMPL  void*  cvAlloc( size_t size )
{
    void* ptr = 0;
    
    CV_FUNCNAME( "cvAlloc" );

    __BEGIN__;

    if( (size_t)size > CV_MAX_ALLOC_SIZE )                // 限制        
        CV_ERROR( CV_StsOutOfRange,
                  "Negative or too large argument of cvAlloc function" );

    ptr = p_cvAlloc( size, p_cvAllocUserData );           // 报错
    if( !ptr )
        CV_ERROR( CV_StsNoMem, "Out of memory" );

    __END__;

    return ptr;
}

        按照zbf661 推荐的注释掉限制条件之后，重新编译，打开尺寸为28012*18251的图像，还是有问题，但是zbf661 的测试代码可行：

IPlImage * img = cvCreateImage( cvSize ( 20000 , 20000 ) , 8 , 3 );
cvZero( img ) ; 
cvShowImage( "bigimage" ,img ) ;

        chai2010 推荐大尺寸图片用GDAL扩展库，看看去！