figure, imshow, saveas and getpts

I save an image using saveas. Then I open it and display it using imshow in figure 1. When I use getpts to get pixel coordinates, the coordinates I get are that of figure 1 not that of the image. I.e, If I click on the axis of the image, I don't get (0,0), I get the coordinates of the image origin in figure 1. How do I get the image coordinates?

Answer 1

[Image Analyst]

Save images with imwrite(). Recall them with imread(). Display them with imshow(). Get pixel values with impixelinfo:

hp = impixelinfo();

This will let you mouse around and display the (x,y) and gray level in a status label on your figure. If you need the user to click on a point, then use ginput():

[x, y] = ginput();

[Douglas Brenner]

No. impixelinfo still reads pixels in the figure but outside the image. Same for ginput and getpts

[Douglas Brenner]

Cockpit error. I can get the right coordinates. However, imshow does not show the image.

[Image Analyst]

Your image may be floating point. Use []:

imshow(yourImage, []);

[Douglas Brenner]

Got it. You have to write and read it as uint8

[Image Analyst]

Yes, for most standard image formats. Or you could use uint16. If you want to keep as floating point instead of integers, use save() to save as a .mat file, then use load() to recall it.

Answer 2

[Ramesh Bala]

but in this case [x,y] = getpts

x =

118.5645
242.4355

y =

199.6316
197.2105

its giving both x1y1 and x2 y2...how to get only x1x2

[Image Analyst]

You already have that in your x variable.