Paint on Image MATLAB - image

Question

Basically, I have a matrix filled with 0's and 1's that is a representation of an image. I essentially want a GUI that allows me to arbitrarily draw or make lines on the image, so essentially, Microsoft paint capabilities of drawing on the image.
Thanks for all your help.

Answer 1

As I commented, you can use ginput.
Here is a short program you can test.
fh = figure;
imageh = imshow(false(50));
% Create a button in the figure.
uicontrol('Parent',fh,'Style','pushbutton','String','paint','Callback',{#paintButtonCallback, imageh});
% button callback function
function paintButtonCallback(~,~,imageh)
[x,y] = ginput(1);
% round the values so they can be used for indexing.
x = round(x);
y = round(y);
% make sure the values do not go outside the image.
s = size(imageh.CData);
if x > s(2) || y > s(1) || x < 1 || y < 1
return
end
% make the selected pixel white.
imageh.CData(round(y),round(x)) = true;
end
Update
I'm not sure if there is any existing toolbox would allow you to edit images as conveniently as you can with MS paint. However, it is possible to code it yourselves.
To draw a line you can use 'ginput(2)' to take two points and plot the line. Note that the findLine function isn't perfect.
[x,y] = ginput(2);
% find all pixels on the line xy
ind = findLine(size(imageh.CData),x,y);
% make the selected pixel white.
imageh.CData(ind) = true;
function [x,y] = findLine(x,y)
% Find all pixels that lie between points defined by [x(1),y(1)] and [x(2),y(2)].
supersampling = 1.2;
[x,y,~] = improfile(s,round(x),round(y),max([diff(x);diff(y)])*supersampling);
ind = sub2ind(s,round(x),round(y));
end
If you have Image Processing Toolbox, you have the option to use drawline, which gives a better draw experience and you can get the pixels on the line using createMask function:
h = drawline;
ind = h.createMask;
drawfreehand may be also relevant:
h = drawfreehand;
x = h.Position(:,1);
y = h.Position(:,2);
You can delete the object created on the image with delete(h) if you don't need it. See more similar functions in MATLAB documentation.
It is also painful when you have to click the paint button each time you need to paint a point. To overcome this problem, you can use the ButtonDownFcn of the figure. The paint button will update the ButtonDownFcn with a meaningful callback or empty value depending on the circumstance:
function paintButtonCallback(obj,~,imageh)
if isempty(obj.Tag)
imageh.ButtonDownFcn = #paintMode;
obj.Tag = 'on';
else
imageh.ButtonDownFcn = '';
obj.Tag = '';
end
And the meaningful callback paintMode:
function paintMode(~,~)
[x,y] = ginput(1);
% round the values so they can be used for indexing.
x = round(x);
y = round(y);
% make sure the values do not go outside the image.
s = size(imageh.CData);
if x > s(2) || y > s(1) || x < 1 || y < 1
return
end
% make the selected pixel white.
imageh.CData(y,x) = true;
end
The full demo code:
fh = figure;
imageh = imshow(false(20));
% Create buttons in the figure.
uicontrol('Parent',fh,'Style','pushbutton','String','paint','Callback',{#paintButtonCallback, imageh});
bh = uicontrol('Parent',fh,'Style','pushbutton','String','line','Callback',{#lineButtonCallback, imageh});
bh.Position(2) = 50;
bh2 = uicontrol('Parent',fh,'Style','pushbutton','String','line2','Callback',{#line2ButtonCallback, imageh});
bh2.Position(2) = 80;
bh3 = uicontrol('Parent',fh,'Style','pushbutton','String','free','Callback',{#freeButtonCallback, imageh});
bh3.Position(2) = 110;
% button callback function
function paintButtonCallback(obj,~,imageh)
if isempty(obj.Tag)
imageh.ButtonDownFcn = #paintMode;
obj.Tag = 'on';
else
imageh.ButtonDownFcn = '';
obj.Tag = '';
end
function paintMode(~,~)
[x,y] = ginput(1);
% round the values so they can be used for indexing.
x = round(x);
y = round(y);
% make sure the values do not go outside the image.
s = size(imageh.CData);
if x > s(2) || y > s(1) || x < 1 || y < 1
return
end
% make the selected pixel white.
imageh.CData(y,x) = true;
end
end
% button callback function
function lineButtonCallback(~,~,imageh)
% take two points at a time
[x,y] = ginput(2);
% make sure the values do not go outside the image.
s = size(imageh.CData);
if any(x > s(2)+0.5 | y > s(1)+0.5 | x < 0.5 | y < 0.5) || (diff(x) == 0 && diff(y) == 0)
return
end
% find all pixels on the line xy
ind = findLine(size(imageh.CData),x,y);
% make the selected pixel white.
imageh.CData(ind) = true;
end
function ind = findLine(s,x,y)
% Find all pixels that lie between points defined by [x(1),y(1)] and [x(2),y(2)].
supersampling = 1.2;
[x,y,~] = improfile(s,round(x),round(y),max([diff(x);diff(y)])*supersampling);
ind = sub2ind(s,round(x),round(y));
end
% button callback function
function line2ButtonCallback(~,~,imageh)
% take two points at a time
h = drawline;
ind = h.createMask;
delete(h);
% make the selected pixel white.
imageh.CData(ind) = true;
end
% button callback function
function freeButtonCallback(~,~,imageh)
% take two points at a time
h = drawfreehand;
x = h.Position(:,1);
y = h.Position(:,2);
delete(h);
ind = sub2ind(size(imageh.CData),round(y),round(x));
% make the selected pixel white.
imageh.CData(ind) = true;
end