Discussion :

[hamska2]

Bonjour,
Avec la fonction cvDft j applique une transformée de fourrier sur une image 8 bit en niveau de gris et lorsque j'applique la cvDft inverse je n'obtiens pas l'image d'origine sachant que je n'ai retiré aucun coefficient après la transformée directe.
Quelqu'un a une explication ?
Merci

[hamska2]

Voici le bout de code que j'utilise :

Code :

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IplImage *dst= cvCreateImage(cvGetSize(src),IPL_DEPTH_8U, 1);
	IplImage* realInput = cvCreateImage( cvGetSize(src), IPL_DEPTH_64F, 1);
	IplImage* imaginaryInput = cvCreateImage( cvGetSize(src), IPL_DEPTH_64F, 1);
	IplImage* complexInput = cvCreateImage( cvGetSize(src), IPL_DEPTH_64F, 2);		
	int dft_M = cvGetOptimalDFTSize( src->height - 1 );
	int dft_N = cvGetOptimalDFTSize( src->width - 1 );
	CvMat* dft_A = cvCreateMat( dft_M, dft_N, CV_64FC2 );
 
 
	IplImage* image_Re = cvCreateImage( cvSize(dft_N, dft_M), IPL_DEPTH_64F, 1);
	IplImage* image_Im = cvCreateImage( cvSize(dft_N, dft_M), IPL_DEPTH_64F, 1);
 
 
	cvScale(src, realInput, 1.0, 0.0);
	cvZero(imaginaryInput);
	cvMerge(realInput, imaginaryInput, NULL, NULL, complexInput);
 
	// copy A to dft_A 
 
	cvGetSubRect( dft_A, &tmp, cvRect(0,0, src->width,src->height));
	cvCopy( complexInput, &tmp, NULL );
	cvGetSubRect( dft_A, &tmp, cvRect(src->width,0, src->cols - src->width, src->height));
 
	if ((dft_A->cols - src->width) > 0)			  
	{
		cvZero( &tmp );
	}	
	// Fourier transform
	cvDFT( dft_A, dft_A, CV_DXT_FORWARD, complexInput->height );
 
	// Inverse Fourier transform
	cvDFT( dft_A, dft_A, CV_DXT_INVERSE , complexInput->height );
 
	cvGetSubRect( dft_A, &tmp, cvRect(0,0, src->width,src->height));
 
	// Split Fourier in real and imaginary parts
	cvSplit( dft_A, image_Re, image_Im, 0, 0 );
 
	// scale image for display
	cvMinMaxLoc(image_Re, &m, &M, NULL, NULL, NULL);
	cvScale(image_Re, image_Re, 1.0/(M-m), 1.0*(-m)/(M-m));
 
	image_Re->origin = src->origin;
 
 
	for(i=0;i<dst->height;i++)
	{
		for(j=0;j<dst->width;j++)
		{
			dst->imageData[j+(i*dst->width)]=(unsigned char)((255)*(((double*)image_Re->imageData)[(j+(image_Re->width-dst->width)/2)+((i+(image_Re->height-dst->height)/2)*(image_Re->width))]));//(unsigned char)(min(255*(((double*)image_Re->imageData)[(j+(image_Re->width-dst->width)/2)+((i+(image_Re->height-dst->height)/2)*(image_Re->width))]),255));
		}
	}
 
	cvSaveImage("src.bmp",src);
	cvSaveImage("dst.bmp",dst);
	// Compute differences image
	cvSub(src,dst,dst,0);
	cvSaveImage("difference.bmp",dst);

[hamska2]

voici le code corrigé :
Une ligne s'était glissée dedans et avait généré cette erreur et donc maintenant ça marche :

Code :

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IplImage *dst= cvCreateImage(cvGetSize(src),IPL_DEPTH_8U, 1);
	IplImage* realInput = cvCreateImage( cvGetSize(src), IPL_DEPTH_64F, 1);
	IplImage* imaginaryInput = cvCreateImage( cvGetSize(src), IPL_DEPTH_64F, 1);
	IplImage* complexInput = cvCreateImage( cvGetSize(src), IPL_DEPTH_64F, 2);		
	int dft_M = cvGetOptimalDFTSize( src->height - 1 );
	int dft_N = cvGetOptimalDFTSize( src->width - 1 );
	CvMat* dft_A = cvCreateMat( dft_M, dft_N, CV_64FC2 );
 
 
	IplImage* image_Re = cvCreateImage( cvSize(dft_N, dft_M), IPL_DEPTH_64F, 1);
	IplImage* image_Im = cvCreateImage( cvSize(dft_N, dft_M), IPL_DEPTH_64F, 1);
 
 
	cvScale(src, realInput, 1.0, 0.0);
	cvZero(imaginaryInput);
	cvMerge(realInput, imaginaryInput, NULL, NULL, complexInput);
 
	// copy A to dft_A 
 
	cvGetSubRect( dft_A, &tmp, cvRect(0,0, src->width,src->height));
	cvCopy( complexInput, &tmp, NULL );
	cvGetSubRect( dft_A, &tmp, cvRect(src->width,0, src->cols - src->width, src->height));
 
	if ((dft_A->cols - src->width) > 0)			  
	{
		cvZero( &tmp );
	}	
	// Fourier transform
	cvDFT( dft_A, dft_A, CV_DXT_FORWARD, complexInput->height );
 
	// Inverse Fourier transform
	cvDFT( dft_A, dft_A, CV_DXT_INVERSE , complexInput->height );
 
	// Split Fourier in real and imaginary parts
	cvSplit( dft_A, image_Re, image_Im, 0, 0 );
 
	// scale image for display
	cvMinMaxLoc(image_Re, &m, &M, NULL, NULL, NULL);
	cvScale(image_Re, image_Re, 1.0/(M-m), 1.0*(-m)/(M-m));
 
	image_Re->origin = src->origin;
 
 
	for(i=0;i<dst->height;i++)
	{
		for(j=0;j<dst->width;j++)
		{
			dst->imageData[j+(i*dst->width)]=(unsigned char)((255)*(((double*)image_Re->imageData)[(j+(image_Re->width-dst->width)/2)+((i+(image_Re->height-dst->height)/2)*(image_Re->width))]));//(unsigned char)(min(255*(((double*)image_Re->imageData)[(j+(image_Re->width-dst->width)/2)+((i+(image_Re->height-dst->height)/2)*(image_Re->width))]),255));
		}
	}
 
	cvSaveImage("src.bmp",src);
	cvSaveImage("dst.bmp",dst);
	// Compute differences image
	cvSub(src,dst,dst,0);
	cvSaveImage("difference.bmp",dst);

[Nessros]

Bonjour,

Est-ce que c'est possible de poster tout le programme svp.

Merci