Extracting actual pixel number from `ginput()`

Question

I am using the following code on a given image:

imshow(image);
[out1,out2]=ginput(1);

I am getting a non-integer relative number.

• How do I extract the exact pixel numbers in (row,column) from the output of ginput().
• I want to, later on, generate an affine transformation matrix (using estimateGeometricTransform()) to move points in one image to a second image. should I use the pixel number or the regular output of ginput()?

Answer 1

ginput gives you relative positions, so

round(ginput(1))

should get you to the centre of the pixel, which is what you'll probably want, as it's difficult to select matching features on a level finer than pixels. If you can select features on a level finer than pixels, you should of course use that, and do that for both images.