trouble passing image from c to matlab..

2011 5 11
2 个回答
7 次查看（30 天）

0 个投票

...
mxArray *mat1;
UINT8_T *dynamicData;
mwSize index;
unsigned long int elements;
elements = (ImgTempTp->width)*(ImgTempTp->height);
dynamicData = mxCalloc(elements, sizeof(UINT8_T));
for ( index = 0; index < elements; index++ ) {
dynamicData[index] = ImgTempTp->imageData[index];
}
mat1 = mxCreateNumericMatrix(0, 0, mxUINT8_CLASS, mxREAL);
mxSetData(mat1, dynamicData);
mxSetM(mat1, ImgTempTp->height);
mxSetN(mat1, ImgTempTp->width);
mlfShowimage(mat1);
.
.
ImgTempTp is an image created by opencv. the data type is unsigned char.
function [] = showimage(img)
figure,imshow(img);
input('Press Enter to continue...');
end
Some times the image appears properly but many times it gets mixed up in 2-3 manners i.e. it has 2-3 sections which contains parts of original image in tilted fashion
I have tried memcpy also. But i get the same error.. PLs help...

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Vikash Anand
Vikash Anand 2011-5-11
If i try loading an image using cvLoadImage in opencv and then pass it to matlab, i get different images at each run.
Also, the distorted image has max. no. of sections as 4.
Vikash Anand
Vikash Anand 2011-5-11
result :
https://sites.google.com/site/scrapfromvks/matlab
these images have been captured by opencv haar detect and passed on to matlab.. Opencv displays all of these correctly.

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回答（2 个）

Kaustubha Govind
Kaustubha Govind 2011-5-11

0 个投票

Is there a reason your are using a rather roundabout way to achieve this? Why not use something like:
...
mxArray *mat1;
UINT8_T *dynamicData;
mwSize index;
unsigned long int elements;
elements = (ImgTempTp->width)*(ImgTempTp->height);
mat1 = mxCreateNumericMatrix(ImgTempTp->height, ImgTempTp->width, mxUINT8_CLASS, mxREAL);
dynamicData = (UINT8_T *)mxGetData(mat1);
for ( index = 0; index < elements; index++ ) {
dynamicData[index] = ImgTempTp->imageData[index];
}
mlfShowimage(mat1);
.
.
Do you know if ImgTempTp->imageData contains the image in the right indexing order? It seems like the image is being read along the diagonal. Have you tried examining the contents of ImgTempTp->imageData and comparing them with the value 'img' that's passed into showimage?

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Vikash Anand
Vikash Anand 2011-5-11
Thanx for your reply, but this too didn't work... :( ..
the images i have uploaded seem to have a pattern in error : proper image/3 sections for images with "even" dimensions and 2/4 sections for "odd" dimensions.
Amazingly, if i create an opencv structure and copy the data from "mat1" to it, opencv displays it properly ..
unsigned char *dest,*src;
IplImage*ImgTest = cvCreateImage(cvSize(ImgTemp->height,ImgTemp->width),IPL_DEPTH_8U,1); /*dimensions of temp interchanged for transposing*/
bytescount = (ImgTempTp->width)*(ImgTempTp->height)*sizeof(char)
src = (unsigned char *)mxGetPr(mat1);
dest = (uchar *)(ImgTest->imageData);
for(j=0;j< bytescount;j++)
{
dest[j] = src[j];
}
cvShowImage("EBGM Debug",ImgTempTp);
cvWaitKey(2000);
ignore the transpose...
Vikash Anand
Vikash Anand 2011-5-11
The first round about manner i found in "arrayFillSetData.c" in matlab examples.. so just followed it.
Before that, i also tried:
mxArray *mat1;
mwSize dims[2];
dims[0] = (mwSize)(ImgTempTp->width);
dims[1] = (mwSize)(ImgTempTp->height);
mat1 = mxCreateNumericArray(2,dims,mxUINT8_CLASS,mxREAL);
memcpy(mxGetPr(mat1), (uchar *)(ImgTempTp->imageData), (ImgTempTp->width)*(ImgTempTp->height)*sizeof(char));
mlfShowimage(mat1);
but none of these worked !! :(
Kaustubha Govind
Kaustubha Govind 2011-5-11
Could it be than opencv is somehow not storing the pixel values in the expected linear order?

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Vikash Anand
Vikash Anand 2011-5-13

0 个投票

Hey govinda.. i found the solution .. It is something related to 4 bytes alignment. I resized the image in opencv before transferring to matlab such that the dimensions were multiple of 4 and it worked perfectly !!! :)

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