imwrite
Write image to graphics file
Description
imwrite( writes
image data A,filename)A to the file specified by filename,
inferring the file format from the extension. imwrite creates the new
file in your current folder. The bit depth of the output image depends on the data type of
A and the file format. For most formats:
If
Ais of data typeuint8, thenimwriteoutputs 8-bit values.If
Ais of data typeuint16and the output file format supports 16-bit data (JPEG, PNG, and TIFF), thenimwriteoutputs 16-bit values. If the output file format does not support 16-bit data, thenimwritereturns an error.If
Ais a grayscale or RGB color image of data typedoubleorsingle, thenimwriteassumes that the dynamic range is [0, 1] and automatically scales the data by 255 before writing it to the file as 8-bit values. If the data inAissingle, convertAtodoublebefore writing to a GIF or TIFF file.If
Ais of data typelogical, thenimwriteassumes that the data is a binary image and writes it to the file with a bit depth of 1, if the format allows it. BMP, PNG, or TIFF formats accept binary images as input arrays.
If A contains indexed image data, you should additionally specify the
map input argument.
imwrite(
writes the indexed image in A,map,filename)A and its associated colormap
map to the file specified by filename.
If
Ais an indexed image of data typedoubleorsingle, thenimwriteconverts the indices to zero-based indices by subtracting 1 from each element, and then writes the data asuint8. If the data inAissingle, convertAtodoublebefore writing to a GIF or TIFF file.
imwrite(___,
specifies additional parameters for output GIF, HDF, JPEG, PBM, PGM, PNG, PPM, and TIFF
files, using one or more name-value arguments. For example, you can add a comment to an
image in PNG format.Name,Value)
Examples
Write a 50-by-50 array of grayscale values to a PNG file in the current folder.
A = rand(50);
imwrite(A,"myGray.png")Write an indexed image array and its associated colormap to a PNG file.
Load sample image data from the file earth.mat.
load earth.matThe image array X and its associated colormap map are loaded into the workspace.
Write the data to a new PNG file.
imwrite(X,map,"myearth.png")imwrite creates the file myearth.png in your current folder.
View the new PNG file using imshow.
imshow("myearth.png")
Write image data to a new PNG file with the built-in MATLAB® colormap copper.
Load sample image data from the file earth.mat.
load earth.matThe image array X and its associated colormap map are loaded into the workspace. map is a matrix of 64 RGB vectors.
Create a copper-tone colormap with 64 RGB vectors. Then write the image data to a PNG file using the new colormap.
newmap = copper(64);
imwrite(X,newmap,"copperearth.png");imwrite creates the file copperearth.png in your current folder.
View the new PNG file using imshow.
imshow("copperearth.png")
Create and write truecolor image data to a JPEG file.
Create a 49-by-49-by-3 array of random RGB values.
A = rand(49,49,3);
Write the image data to a JPEG file. imwrite automatically chooses this format when you use the .jpg file extension. Add a comment to the file using the Comment name-value argument.
imwrite(A,"newImage.jpg","Comment","My JPEG file")
View information about the new file.
info = imfinfo("newImage.jpg");
info.ColorTypeans = 'truecolor'
[info.Height,info.Width,info.NumberOfSamples,info.BitDepth]
ans = 1×4
49 49 3 24
info.Comment
ans = 1×1 cell array
{'My JPEG file'}
Write multiple images to a single multipage TIFF file.
Create two sets of random image data, im1 and im2.
im1 = rand(50,40,3); im2 = rand(50,50,3);
Write the first image to a new TIFF file. Then, append the second image to the same file.
imwrite(im1,"myMultipageFile.tiff") imwrite(im2,"myMultipageFile.tiff","WriteMode","append")
Draw a series of plots, capture them as images, and write them into one animated GIF file.
Plot for .
x = 0:0.01:1; n = 3; y = x.^n; plot(x,y,LineWidth=3) title("$y = x^n$, $n = $" + num2str(n),Interpreter="latex")
Capture a series of plots for increasing values of .
n = 1:0.5:5; nImages = length(n); fig = figure; for idx = 1:nImages y = x.^n(idx); plot(x,y,LineWidth=3) title("$y = x^n$, $n = $" + num2str(n(idx)),Interpreter="latex") drawnow frame = getframe(fig); im{idx} = frame2im(frame); end close;
Display the series of images in one figure.
figure; for idx = 1:nImages subplot(3,3,idx) imshow(im{idx}); end
Save the nine images into a GIF file. Because three-dimensional data is not supported for GIF files, call rgb2ind to convert the RGB data in the image to an indexed image A with a colormap map. To append multiple images to the first image, call imwrite with the name-value argument WriteMode set to "append".
filename = "testAnimated.gif"; % Specify the output file name for idx = 1:nImages [A,map] = rgb2ind(im{idx},256); if idx == 1 imwrite(A,map,filename,"gif",LoopCount=Inf, ... DelayTime=1) else imwrite(A,map,filename,"gif",WriteMode="append", ... DelayTime=1) end end
imwrite writes the GIF file to your current folder. Setting LoopCount to Inf causes the animation to loop continuously. Setting DelayTime to 1 specifies a 1-second delay between the display of each image in the animation.
