Write an image to a graphics file
Synopsis
imwrite(A,filename,fmt)
imwrite(X,map,filename,fmt)
imwrite(...,filename)
imwrite(...,Parameter,Value,...)
Description
imwrite(A,filename,fmt) writes the image in A to filename. filename is a string that specifies the name of the output file, and fmt is a string that specifies the format of the file. If A is a grayscale intensity image or a truecolor (RGB) image of class uint8, imwrite writes the actual values in the array to the file. If A is of class double, imwrite rescales the values in the array before writing, using uint8(round(255*A)). This operation converts the floating-point numbers in the range [0, 1] to 8-bit integers in the range [0, 255].
This table lists the possible values for fmt:
Format
|
File type
|
'bmp'
|
Windows Bitmap (BMP)
|
'hdf'
|
Hierarchical Data Format (HDF)
|
'jpg' or 'jpeg'
|
Joint Photographers Expert Group (JPEG)
|
'pcx'
|
Windows Paintbrush (PCX)
|
'tif' or 'tiff'
|
Tagged Image File Format (TIFF)
|
'xwd'
|
X Windows Dump (XWD)
|
imwrite(X,map,filename,fmt) writes the indexed image in X, and its associated colormap map, to filename. If X is of class uint8, imwrite writes the actual values in the array to the file. If X is of class double, imwrite offsets the values in the array before writing, using uint8(X-1). map must be of class double; imwrite rescales the values in map using uint8(round(255*map)).
imwrite(...,filename) writes the image to filename, inferring the format to use from the filename's extension. The extension must be one of the legal values for fmt.
imwrite(...,Parameter,Value,...) specifies parameters that control various characteristics of the output file. Parameters are currently supported for HDF, JPEG, and TIFF files.
This table describes the available parameters for HDF files:
Parameter
|
Values
|
Default
|
'Compression'
|
One of these strings: 'none', 'rle', 'jpeg'
|
'rle'
|
'Quality'
|
A number between 0 and 100; parameter applies only if 'Compression' is 'jpeg'; higher numbers mean quality is better (less image degradation due to compression), but the resulting file size is larger
|
75
|
'WriteMode'
|
One of these strings: 'overwrite', 'append'
|
'overwrite'
|
This table describes the available parameters for JPEG files:
Parameter
|
Values
|
Default
|
'Quality'
|
A number between 0 and 100; higher numbers mean quality is better (less image degradation due to compression), but the resulting file size is larger
|
75
|
This table describes the available parameters for TIFF files:
Parameter
|
Values
|
Default
|
'Compression'
|
One of these strings: 'none', 'packbits', 'ccitt'; 'ccitt' is valid for binary images only
|
'ccitt' for binary images; 'packbits' for all other images
|
'Description'
|
Any string; fills in the ImageDescription field returned by imfinfo
|
empty
|
This table summarizes the types of images that imwrite can write:
Format
|
Variants
|
BMP
|
8-bit and 24-bit uncompressed images
|
HDF
|
8-bit raster image datasets, with or without associated colormap; 24-bit raster image datasets
|
JPEG
|
Baseline JPEG images
|
PCX
|
8-bit images
|
TIFF
|
Baseline TIFF images, including 1-bit, 8-bit, and 24-bit uncompressed images; 1-bit, 8-bit, and 24-bit images with packbit compression; 1-bit images with CCITT compression
|
XWD
|
8-bit ZPixmaps
|
Example
imwrite(X,map,'eggs.hdf','Compression','none','WriteMode','append')
See Also
imfinfo, imread
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