MATLAB: Y position of a rectangle drawn over an image compared to axes

axesimage processingrectangle

In the documentation, it states for drawrectangle or rectangle that the position of a rectangle is given by [xmin ymin width height].

If you plot a rectangle over axes, the ymin seems to correspond to the minimum y position from the bottom, but if you do it over an image it appears that the ymin is from the top of the image. Is this correct? Is there a reason for this?

Best Answer

Depending on the state of the axes (hold on or not) and the image drawing function you use, it is common for the image drawing functions to automatically set YDir to 'reverse', because it is common that people want (1,1) of the data array to correspond to the top left corner.

Related Solutions

MATLAB: Draw rectangle in subplot image.

%this draws rectangle on top of I1

subplot(1, 2, 1); % Focus is with axes #1.

imshow(I1, [])
rectangle('Position',[x,y,w,h])
%somewhere else after the above code
%this draws  the rectangle on top of I2
subplot(1, 2, 2); % Focus is with axes #2.
imshow(I2, [])
rectangle('Position',[x,y,w,h])
% Back to #1 now.
%this draws rectangle on top of I1
subplot(1, 2, 1); % Focus is with axes #1.
rectangle('Position',[x,y,w,h])

MATLAB: Rotating a circle drawn using rectangle()

You cannot rotate the circles drawn by rectangle(). Even if you could, you would not notice any difference since they're circles.

You said you know how to change the position so if you were not rotating them about their centers, but about some other location, then you know how to do that - you said so. You just calculate the new upper left coordinate and call rectangle with an updated 'Position' vector. So it's not the location of the circle you're asking about, it's the rotation at a given location, and like I said, you can't do that, nor would you notice any difference even if you could.

Best Answer

Related Solutions

MATLAB: Draw rectangle in subplot image.

MATLAB: Rotating a circle drawn using rectangle()

Related Question