how to add grid to imagesc?

Question

Rabih Sokhen 2022-1-10

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1625865-how-to-add-grid-to-imagesc

评论： DGM 2024-5-13

clear all
clc
a=rand(20,50)
x=linspace(-1,1,20)
y=linspace(-1,1,50)
imagesc(x,x,a)

I would like to add grid only at the border of every pixel in a way wen I zoom in only the initial grid appear

can someone help me with this.

thank you in advance

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Chandan 2024-5-12

how to make the grid in crop field image

DGM 2024-5-13

What grid in what image?

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Answer 1

DGM 2022-1-11

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1625865-how-to-add-grid-to-imagesc#answer_872465

在 MATLAB Online 中打开

It depends how you want to visualize the data. Tools like imshow() or imagesc() represent the data points at the center of each facet in the displayed image. Tools like pcolor() represent the data at the vertices. If the latter is what you intend, then just use pcolor() instead of imagesc().

If you actually want the matrix represented as an image, then you'll have to create the grid. One way would be to just overlay a mesh plot.

s = [4 5]; % [y x]

xrange = [-1 1]; % imagesc only needs the endpoints

yrange = [-1 1];

a = rand(s);

dx = diff(xrange)/(s(2)-1);

dy = diff(yrange)/(s(1)-1);

xg = linspace(xrange(1)-dx/2,xrange(2)+dx/2,s(2)+1);

yg = linspace(yrange(1)-dy/2,yrange(2)+dy/2,s(1)+1);

hi = imagesc(xrange,yrange,a); hold on

hm = mesh(xg,yg,zeros(s+1));

hm.FaceColor = 'none';

hm.EdgeColor = 'k';

You might try to do it by setting the grid properties of the axes, but you'll have to contend with the ticklabels if you do that.

As to how you make the added grid appear only at certain zoom levels, you'd have to create some sort of custom callback to do that. I'll leave that to someone else.

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DGM 2022-1-14

在 MATLAB Online 中打开

You can try this

s = [4 5]; % [y x]

xrange = [-1 1];

yrange = [-1 1];

a = rand(s);

dx = diff(xrange)/(s(2)-1);

dy = diff(yrange)/(s(1)-1);

xg = linspace(xrange(1)-dx/2,xrange(2)+dx/2,s(2)+1);

yg = linspace(yrange(1)-dy/2,yrange(2)+dy/2,s(1)+1);

hi = imagesc(xrange,yrange,a); hold on

set(gca,'xtick',xg,'ytick',yg)

grid on

Note that the ticklabels correspond to the ticks, and so are necessarily not aligned with the face centers anymore. Also, if you have a larger image, all the tick labels will end up overlapping and turning into a mess. You'll have to decide how you want to discard them. In this example, I'm discarding everything but every fourth label. This strategy obviously depends heavily on the size of the image, the label size, and the figure size.

figure % reset web-plot

s = [40 50]; % [y x]

xrange = [-1 1];

yrange = [-1 1];

a = rand(s);

dx = diff(xrange)/(s(2)-1);

dy = diff(yrange)/(s(1)-1);

xg = linspace(xrange(1)-dx/2,xrange(2)+dx/2,s(2)+1);

yg = linspace(yrange(1)-dy/2,yrange(2)+dy/2,s(1)+1);

hi = imagesc(xrange,yrange,a); hold on

set(gca,'xtick',xg,'ytick',yg)

grid on

% just skip some labels

xtlold = get(gca,'xticklabels');

xtlnew = repmat({''},numel(xtlold),1);

xtlnew(1:4:end) = xtlold(1:4:end);

set(gca,'xticklabels',xtlnew);

ytlold = get(gca,'yticklabels');

ytlnew = repmat({''},numel(ytlold),1);

ytlnew(1:4:end) = ytlold(1:4:end);

set(gca,'yticklabels',ytlnew);

Rabih Sokhen 2022-1-14

thank you DGM, it works

Kristoffer Walker 2024-1-23

This is a long-standing RSI issue. This seems like a low-hanging fruit that someone could easily create an API for to make it so much easier for those of us who use and love imagesc. Just add the property "grid", "on". How hard can it be?

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