edgecolor of pixels of imagesc

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'?

Answer 1

[Image Analyst]

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().

Answer 2

[Aaron T. Becker's Robot Swarm Lab]

Consider using the code Pixel Grid, https://www.mathworks.com/matlabcentral/fileexchange/71622-pixel-grid

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.

Answer 3

[Rongxing Hu]

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

[DGM]

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