imwrite
Write image to graphics file
Syntax
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(___, writes
the image in the format specified by fmt)fmt, regardless
of the file extension in filename. You can specify fmt after
the input arguments in any of the previous syntaxes.
imwrite(___, specifies
additional parameters for output GIF, HDF, JPEG, PBM, PGM, PNG, PPM,
and TIFF files, using one or more name-value pair arguments. You can
specify Name,Value)Name,Value after the input arguments in
any of the previous syntaxes.
Examples
Write Grayscale Image to PNG
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 Indexed Image Data to PNG
Write an indexed image array and its associated colormap to a PNG file.
Load sample image data from the file, clown.mat.
load clown.matThe image array X and its associated colormap, map,
are loaded into the MATLAB® workspace.
Write the data to a new PNG file.
imwrite(X,map,'myclown.png')imwrite creates the file, myclown.png,
in your current folder.
View the new file by opening it outside of MATLAB.
Write Indexed Image with MATLAB Colormap
Write image data to a new PNG file with the
built-in MATLAB colormap, copper.
Load sample image data from the file clown.mat.
load clown.matThe image array X and its associated colormap, map,
are loaded into the MATLAB workspace. map is
a matrix of 81 RGB vectors.
Define a copper-tone colormap with 81 RGB vectors. Then, write the image data to a PNG file using the new colormap.
newmap = copper(81);
imwrite(X,newmap,'copperclown.png');imwrite creates the file, copperclown.png,
in your current folder.
View the new file by opening it outside of MATLAB.
Write Truecolor Image to JPEG
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); A(:,:,2) = rand(49,49); A(:,:,3) = rand(49,49);
Write the image data to a JPEG file, specifying the output
format using 'jpg'. Add a comment to the file using
the 'Comment' name-value pair argument.
imwrite(A,'newImage.jpg','jpg','Comment','My JPEG file')
View information about the new file.
imfinfo('newImage.jpg')ans =
Filename: 'S:\newImage.jpg'
FileModDate: '25-Jan-2013 16:18:41'
FileSize: 2339
Format: 'jpg'
FormatVersion: ''
Width: 49
Height: 49
BitDepth: 24
ColorType: 'truecolor'
FormatSignature: ''
NumberOfSamples: 3
CodingMethod: 'Huffman'
CodingProcess: 'Sequential'
Comment: {'My JPEG file'}Write Multiple Images to TIFF 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.tif') imwrite(im2,'myMultipageFile.tif','WriteMode','append')
Write Animated GIF
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) ])
Capture a series of plots for increasing values of
.
n = 1:0.5:5; nImages = length(n); figure; for idx = 1:nImages y = x.^n(idx); plot(x,y,'LineWidth',3) title(['y = x^n, n = ' num2str( n(idx)) ]) drawnow frame = getframe(1); 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 pair argument 'WriteMode','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. Name-value pair 'LoopCount',Inf causes the animation to continuously loop. 'DelayTime',1 specifies a 1-second delay between the display of each image in the animation.