imshow — Display images in MATLAB and RunMat.
imshow displays grayscale, binary, and truecolor image data with MATLAB-style defaults. File-input handling and display scaling behavior follow MATLAB semantics.
Syntax
h = imshow(I)
h = imshow(I, [low high])
h = imshow(I, [])Inputs
| Name | Type | Required | Default | Description |
|---|---|---|---|---|
I | Any | Yes | — | Image matrix/array or filename. |
I | Any | Yes | — | Numeric grayscale image matrix/array. |
DisplayRange | NumericArray | Yes | [] | Display limits as [] or [low high]. |
Returns
| Name | Type | Description |
|---|---|---|
h | NumericScalar | Handle to the image object. |
Errors
| Identifier | When | Message |
|---|---|---|
RunMat:imshow:InvalidArgument | Image input, filename, or display range arguments are malformed or unsupported. | imshow: invalid argument |
RunMat:imshow:Internal | Internal image decoding or render preparation fails unexpectedly. | imshow: internal operation failed |
How imshow works
imshow(I)displays 2-D numeric data with grayscale limits[0, 1], matching MATLAB double-image defaults.imshow(BW)displays logical image data as black and white using[0, 1]limits.imshow(RGB)displays MxNx3 truecolor data directly.- In
runmatcompatibility mode,imshow(RGBA)accepts supported numeric MxNx4 data as a RunMat extension and displays its fourth channel as alpha. imshow(I, [low high])displays grayscale image data using an explicit display range.imshow(I, [])auto-scales grayscale image data from finite minimum to finite maximum.imshow(filename)reads and decodes an image file, then displays it as truecolor data.
Examples
Display a simple grayscale image
row = 100;
col = 100;
rsm = ones(row, col);
imshow(rsm);Auto-scale a matrix for display
A = peaks(128);
imshow(A, []);Display truecolor RGB data
R = ones(64, 64);
G = zeros(64, 64);
B = zeros(64, 64);
RGB = cat(3, R, G, B);
imshow(RGB);Display an image file
imshow("photo.png");Rendered imshow example
[X, Y] = meshgrid(linspace(-3, 3, 220), linspace(-2, 2, 150));
field = exp(-0.8*((X-1).^2 + Y.^2)) - 0.7*exp(-((X+1).^2 + (Y-0.4).^2));
imshow(field, []);
title('Autoscaled Grayscale Field');
Compare this result with other chart types in the MATLAB Plot Gallery.
Using imshow with coding agents
Open a RunMat example with live inputs, then ask the agent to explain how imshow changes the result.
Run a small imshow example, explain the result, then change one input and compare the output.
FAQ
What display range does imshow use for doubles?⌄
imshow(I) uses [0, 1] for floating-point grayscale data. Use imshow(I, []) when you want RunMat to scale the visible range from the data minimum to maximum.
Does imshow support uint8 and uint16 image defaults?⌄
Yes. Grayscale uint8 data uses [0, 255], grayscale uint16 data uses [0, 65535], and truecolor data of either class is normalized by the corresponding full-scale value.
How is imshow different from imagesc?⌄
imshow is for image display and uses grayscale or truecolor image defaults. imagesc is for scaled matrix visualization and maps data through the active colormap.
Related Plotting functions
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Open-source implementation
Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how imshow is executed, line by line, in Rust.
- View the source for imshow in Rust on GitHub
- Learn how the RunMat runtime works
- Found a bug? Open an issue with a minimal reproduction.
About RunMat
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