how can i access to element of an image and modify it

[iman_kh]

hi
i want to modify cells of image
how can i access to element of an image and modify it
so thanks

[canming]

It's Simple. If you have an image

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Image<Bgr^, Byte>^ img;

You can obtain the value on the (x, y) position by calling

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Bgr^ color = img[y,x];

To set the color, call

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img[y,x] = color

[Scissorhands]

Hi, I have the same problem!
I have to tranlsate this C++ OpenCv code

for( int i = 1; i < mask->width-1; i++ )
for( int j = 1; j < mask->height-1; j++ )
{
uchar idx = CV_IMAGE_ELEM( mask, uchar, j, i );
if(idx==255){
uchar blue = CV_IMAGE_ELEM( color_img0, uchar, j-1, (i-1)*3);
uchar green = CV_IMAGE_ELEM( color_img0, uchar, j-1, (i-1)*3 +1);
uchar red = CV_IMAGE_ELEM( color_img0, uchar, j-1, (i-1)*3 +2);
(uchar) CV_IMAGE_ELEM( color_imgSelected, uchar, j-1, (i-1)*3)= blue;
(uchar) CV_IMAGE_ELEM( color_imgSelected, uchar, j-1, (i-1)*3+1)= green;
(uchar) CV_IMAGE_ELEM( color_imgSelected, uchar, j-1, (i-1)*3+2)= red;
}
}

into C# Emgu code. I wrote:

for (int i = 1; i < mask.Width - 1; i++)
for (int j = 1; j < mask.Height - 1; j++)
{
Gray idx = mask[j, i];
if (idx.Intensity == 255)
{
imageSelected[j - 1, (i - 1)] = originalImage[j - 1, (i - 1)];
}

}

It works, but it is very very slow!!!
It seems that accessing pixels takes a lot of time. Instead in Opencv this operation is much more fast!!
Or I do something wrong!

Any help?
Thank you very very much!!!

[Scissorhands]

I solved the problem in this way:

MCvScalar indx = CvInvoke.cvGet2D(mask, j, i);
if (indx.v0 == 255)
{
MCvScalar newColor = CvInvoke.cvGet2D(originalImage, j - 1, i - 1);
CvInvoke.cvSet2D(imageSelected, j - 1, i - 1, newColor);
}

inside the 2 for.
Now it works very fast!!

[canming]

If mask contain only values of either 0 or 255, the following call would be THE FASTEST (and use fewest code):

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imageSelected = originalImage.Copy(mask);

If the mask contains values other than 0 or 255, then apply threshold on the mask first.