Coordinates of the brightest point of the first line

Hello, how can I know the coordinates of the brightest point of the first line of my image?

Can someone help me with this algorithm?

Thank you,

Thiago Tenório

Answer 1

[Walter Roberson]

[minval, minidx] = max(YourImage(:,1));

or

[minval, minidx] = max(YourImage(1,:));

Oh wait -- is this an RGB image or grayscale? If it is RGB then how do you want to define "brightest" ?

[Image Analyst]

Note: Because it's looking at just one row, the (row, column) coordinate is (1, minidx). If you are going to look at brightest points defined in other ways (for a true color image, or for multiple localized (non-global) maxima) or for rows other than the first row, then write back and say so to get solutions for those situations.

[Walter Roberson]

And I've been wondering if the "line" is something that needs to be detected in the image, such as a background with things drawn on it, or through edge detection. Then it would be important to define "first"...

http://www.mathworks.com/matlabcentral/answers/7924-where-can-i-upload-images-and-files-for-use-on-matlab-answers

[Image Analyst]

Good point. In that situation there are several ways to do it, including taking the max of the masked pixels (works for any shape), or taking the max of a profile that you extract with improfile() (if it's really a straight line).

[Thiago Tenorio]

Thanks for the replies!

It is an image of mammography. I have a black background. The idea is to go through the first line starting with the background image to the edge of mammography. I need coordinate of the point where the image begins, ie where the pixel value is different from the background.

[Image Analyst]

I think a histogram would be a better method for determining the gray level between the foreground and the background.

[Walter Roberson]

greythresh() might be suitable.