Read image from graphics file
Synopsis
A = imread(filename,fmt)
[X,map] = imread(filename,fmt)
[...] = imread(filename)
[...] = imread(...,idx)
[...] = imread(...,ref)
Description
A = imread(
filename,fmt)
reads the image in filename into A
, whose class is
uint8
. If the file contains a grayscale intensity image, A
is a two-dimensional array. If the file contains a truecolor (RGB) image, A
is a three-dimensional (m
-by-n
-by-3) array. filename is a string that specifies the name of the graphics file, and fmt
is a string that specifies the format of the file. The file must be in the current directory or in a directory in the MATLAB path. If imread
cannot find a file named filename, it looks for a file named filename
.fmt
.
This table lists the possible values for fmt
:
Format
|
File type
|
'bmp'
|
Windows Bitmap (BMP)
|
'hdf'
|
Hierarchical Data Format (HDF)
|
'jpg' or 'jpeg'
|
Joint Photographic Experts Group (JPEG)
|
'pcx'
|
Windows Paintbrush (PCX)
|
'tif' or 'tiff'
|
Tagged Image File Format (TIFF)
|
'xwd'
|
X Windows Dump (XWD)
|
[X,map] = imread(
filename,fmt)
reads the indexed image in filename into X
and its associated colormap into map
. X
is of class uint8
, and map
is of class double
. The colormap values are rescaled when they are read to have the range [0, 1].
[...] = imfread(
filename)
attempts to infer the format of the file from its content.
[...] = imread(...,idx)
reads in one image from a multi-image TIFF file. idx
is an integer value that specifies the order that the image appears in the file. For example, if idx
is 3, imread
reads the third image in the file. If you omit this argument, imread
reads the first image in the file.
[...] = imread(...,ref)
reads in one image from a multi-image HDF file. ref
is an integer value that specifies the reference number used to identify the image. For example, if ref
is 12, imread
reads the image whose reference number is 12. (Note that in an HDF file the reference numbers do not necessarily correspond with the order of the images in the file.) If you omit this argument, imread
reads the first image in the file.
This table summarizes the types of images that imread
can read:
Format
|
Variants
|
BMP
|
1-bit, 4-bit, 8-bit, and 24-bit uncompressed images; 4-bit and 8-bit run-length encoded (RLE) images
|
HDF
|
8-bit raster image datasets, with or without associated colormap; 24-bit raster image datasets
|
JPEG
|
Any baseline JPEG image; JPEG images with some commonly used extensions
|
PCX
|
1-bit, 8-bit, and 24-bit images
|
TIFF
|
Any baseline TIFF image, 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
|
1-bit and 8-bit ZPixmaps; XYBitmaps; 1-bit XYPixmaps
|
Examples
This example reads the sixth image in a TIFF file:
[X,map] = imread('flower.tif',6);
This example reads the fourth image in an HDF file:
info = imfinfo('skull.hdf');
[X,map] = imread('skull.hdf',info(4).Reference);
See Also
imfinfo
, imwrite
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