edgecolor of pixels of imagesc

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Ankit Labh
Ankit Labh on 25 May 2020
Commented: DGM on 25 May 2022
I want the black edge color for the boundaries of each pixel drawn using imagesc. If I use pcolor, I get the black boundary around pixels. How can I get the same using 'imagesc'?

Answers (3)

Image Analyst
Image Analyst on 25 May 2020
Edited: Image Analyst on 25 May 2020
You can't. And if you use pcolor, you don't either. The tiles you see in pcolor are NOT pixels. Look closely. If you want to show a 4x4 array with pcolor, do you see a 4x4 array of pixels?
m = magic(4)
pcolor(m);
No, you don't. Those black lines goes through the MIDDLE of the pixels, they don't surround them. And to make it worse, you see a 3x3 array of tiles, not a 4x4 array. Very deceiving so that's why I never use pcolor().

Aaron T. Becker's Robot Swarm Lab
The function pixelgrid superimposes a grid of pixel edges on an image. The purpose is to easily visualize pixel extents when zooming in closely on an image. The grid is drawing using lines with contrasting colors so that it is visible regardless of the colors of the underlying pixels.
Cite As
Steve Eddins (2021). Pixel Grid (https://github.com/mathworks/pixelgrid), GitHub. Retrieved January 25, 2021.

Rongxing Hu
Rongxing Hu on 24 May 2022
You could use plot to add the edge lines
edge_x = repmat( [0:length(xdata)]+0.5, length(ydata)+1,1)
edge_y = transpose( repmat( [0:length(ydata)]+0.5, length(xdata)+1,1) )
plot(edge_x ,edge_y, ' k') % vertical lines
hold on
plot( transpose(deg_x), transpose(edge_y ), 'k') % horizontal lines
  1 Comment
DGM
DGM on 25 May 2022
You can use the editor tools to run the example code in-situ to create a more complete demonstration of the code.
m = magic(4)
m = 4×4
16 2 3 13 5 11 10 8 9 7 6 12 4 14 15 1
imagesc(m); hold on
nx = size(m,2);
ny = size(m,1);
edge_x = repmat((0:nx)+0.5, ny+1,1);
edge_y = repmat((0:ny)+0.5, nx+1,1).';
plot(edge_x ,edge_y, ' k') % vertical lines
plot(edge_x.', edge_y.', 'k') % horizontal lines

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