Copy OpenCV IplImage or Mat into Freeimage FIBITMAP - opencv

Question

I need to exchange data between FreeImage (FIBITMAP) and OpenCV format (IplImage and/or Mat). I'm fine with getting data from a FIBITMAP into an IplImage or Mat since FreeImage gives you a function FreeImage_GetScanLine which you can set the OPenCV imageData ptr equal to.
However, I'm stuck on how to do the reverse, i.e. once I have an OpenCV image, how do I get its data into a FreeImage image?

Answer 1

Here is a more detailed code for the conversion. There are many image data types in either library, I tried supporting most common ones. This assumes you are passing a cv::Mat as the source. FreeImage has the view perspective of lower left!
/* These are openCV types
#define CV_8U 0
#define CV_8S 1
#define CV_16U 2
#define CV_16S 3
#define CV_32S 4
#define CV_32F 5
#define CV_64F 6
*/
/* these are FI types
FIT_UNKNOWN = 0, // unknown type
FIT_BITMAP = 1, // standard image : 1-, 4-, 8-, 16-, 24-, 32-bit
FIT_UINT16 = 2, // array of unsigned short : unsigned 16-bit
FIT_INT16 = 3, // array of short : signed 16-bit
FIT_UINT32 = 4, // array of unsigned long : unsigned 32-bit
FIT_INT32 = 5, // array of long : signed 32-bit
FIT_FLOAT = 6, // array of float : 32-bit IEEE floating point
FIT_DOUBLE = 7, // array of double : 64-bit IEEE floating point
FIT_COMPLEX = 8, // array of FICOMPLEX : 2 x 64-bit IEEE floating point
FIT_RGB16 = 9, // 48-bit RGB image : 3 x 16-bit
FIT_RGBA16 = 10, // 64-bit RGBA image : 4 x 16-bit
FIT_RGBF = 11, // 96-bit RGB float image : 3 x 32-bit IEEE floating point
FIT_RGBAF = 12 // 128-bit RGBA float image : 4 x 32-bit IEEE floating point
*/
if(_dib) // get rid of the current dib.
FreeImage_Unload(_dib);
int width = src.size().width;
int height = src.size().height;
switch(src.type())
{
case CV_8U :{_dib = FreeImage_AllocateT(FIT_BITMAP,width, height, 8) ;}break; // 8 bit grayscale
case CV_8UC3:{_dib = FreeImage_AllocateT(FIT_BITMAP,width, height, 24);}break; // 24 bit RGB
case CV_16U :{_dib = FreeImage_AllocateT(FIT_UINT16,width, height, 16);}break; // 16 bit grayscale
case CV_16S :{_dib = FreeImage_AllocateT(FIT_INT16 ,width, height, 16);}break;
case CV_32S :{_dib = FreeImage_AllocateT(FIT_INT32 ,width, height, 32);}break;
case CV_32F :{_dib = FreeImage_AllocateT(FIT_FLOAT ,width, height, 32);}break;
case CV_64F :{_dib = FreeImage_AllocateT(FIT_DOUBLE,width, height, 32);}break;
default:ASSERT(FALSE);
}
if(_dib==NULL)
return FALSE;
int srcRowBytes = width * src.elemSize();
for (int ih=0;ih<height;ih++)
{
BYTE* ptr2Line = FreeImage_GetScanLine(_dib,(height-1)-ih);
memcpy(ptr2Line,src.ptr(ih),srcRowBytes);
}
_bHasChanged = TRUE;
return TRUE;

Answer 2

You have to be a little careful just copying the data pointer, a lot of image formats have padding to start each new line on eg a 4byte boundary.
If your image has a GetScanLine() function then it's probably safer to make an empty plImage*/cv::Mat and memcopy each row with the pointer returned from GetScanLine() and the .ptr() member of cv::MAt
cv::Mat &src
int srcRowBytes = width * src.elemSize();
for (int ih=0;ih<height;ih++) {
memcpy(dest.pointer_to_row(ih),src.ptr(ih),srcRowBytes);
}

Answer 3

Well, if you don't mind the copy, you can just create an IplImage*/cv::Mat header for the FIBITMAP and then copy (using the opencv function), like this:
cv::Mat src; // your source image
FIBITMAP whatever; // allocate space for your FIBITMAP here
cv::Mat wrapper(height, width, CV_8UC3, ptr_from_FIBITMAP, step);
src.copyTo(wrapper);