imwrite
Purpose
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)
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)
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)
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,...)
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 uncompressed images with associated colormap; 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,'flowers.hdf','Compression','none',...
'WriteMode','append')
See Also
imfinfo Return information about a graphics file
imread Read image from graphics file
[ Previous | Help Desk | Next ]