Function Reference

image

Display

image
Display a matrix as a color image.
imagesc
Display a scaled version of the matrix A as a color image.
imshow
Display the image IM, where IM can be a 2-dimensional (gray-scale image) or a 3-dimensional (RGB image) matrix.

Read/write

imread
Read images from various file formats.
imwrite
Write image from octave to various file formats
imfinfo
Read image information from a file.
imginfo
Get image size from file FILENAME.
bmpwrite
Write the bitmap X into FILE (8-bit indexed uncompressed).
jpgread
Read a JPEG file from disk.
jpgwrite
Write a JPEG file to disc.
pngread
Read a PNG file from disk.
pngwrite
Writes a png file to the disk using the Red, Green, Blue and Alpha matrices.

Reshape

imcrop
Not implemented.
imremap
Applies any geometric transformation to the image IM.
imperspectivewarp
Applies the spatial perspective homogeneous transformation P to the image IM.
imresize
Scales the image A by a factor M using nearest neighbour interpolation.
imrotate
Rotation of a 2D matrix about its center.
imrotate_Fourier
Rotation of a 2D matrix.
imtranslate
Translate a 2D image by (x,y) using Fourier interpolation.
imshear
Applies a shear to the image M.
impad
Pad (augment) a matrix for application of image processing algorithms.
padarray
Pads an array in a configurable way.
rotate_scale
Arbitrary rotation and scaling of a gray-scale image using fast bilinear interpolation.

Analysis and Statistics

fftconv2
Convolve 2 dimensional signals using the FFT.
corr2
Returns the correlation coefficient between I and J.
imhist
Shows the histogram of an image using hist.
mean2
Returns the mean value for a 2d real type matrix.
std2
Returns the standard deviation for a 2d real type matrix.
qtdecomp
Performs quadtree decomposition.
qtgetblk
Obtain block values from a quadtree decomposition.
qtsetblk
Set block values in a quadtree decomposition.
graycomatrix
Calculates the gray-level co-occurrence matrix P of a gray-level image IM.
houghtf
Calculate the straight line Hough transform of a binary image I.
graythresh
Compute global image threshold using Otsu's method.

Filtering

colfilt
Apply filter to matrix blocks
fspecial
Create spatial filters for image processing.
histeq
Histogram equalization of a gray-scale image.
imadjust
Adjust image or colormap values to a specified range
imnoise
Adds noise to image in A.
medfilt2
Two dimensional median filtering.
ordfilt2
Two dimensional ordered filtering.
cordflt2
Implementation of two-dimensional ordered filtering.
uintlut
Computes matrix B by using A as an index to lookup table LUT.
stretchlim
Finds limits to contrast stretch an image
makelut
Create a lookup table which can be used by applylut.
applylut
Uses lookup tables to perform a neighbour operation on binary images.
deriche
Return edge detector image of A image according to an algorithm by Rachid Deriche.

Black and white image functions

bwarea
Estimates the area of the "on" pixels of BW.
bwdist
Computes the distance transform of the binary image BW.
bweuler
Calculates the Euler number of a binary image.
bwfill
Perform a flood-fill operation on the binary image BW1.
bwlabel
Labels foreground objects in the binary image BW.
bwmorph
Perform a morphological operation on a binary image.
bwperim
Find the perimeter of objects in binary images.
bwselect
Select connected regions in a binary image.
dilate
Perform a dilation morphological operation on a binary image.
erode
Perform an erosion morphological operation on a binary image.
bwborder
Finds the borders of foreground objects in a binary image.
edge
Find image edges.
conndef
Creates a connectivity array.

Colour controls

cmpermute
Reorders colors in a colormap.
cmunique
Finds colormap with unique colors and corresponding image.
imapprox
Not implemented.
rgb2ycbcr
Not implemented.
ycbcr2rgb
Not implemented.

Representation

dither
Not implemented.
gray2ind
Convert a gray scale intensity image to an Octave indexed image.
grayslice
creates an indexed image X from an intensitiy image I using multiple threshold levels.
im2bw
Converts image data types to a black-white (binary) image.
im2double
Converts the input image to an image of class double.
im2uint8
Converts the input image to an image of class uint8.
im2uint16
Converts the input image to an image of class uint16.
ind2gray
Convert an Octave indexed image to a gray scale intensity image.
ind2rgb
Convert an indexed image to red, green, and blue color components.
isbw
Returns true for a black-white (binary) image.
isgray
Returns true for an gray-scale intensity image.
isind
Returns true for an index image.
isrgb
Returns true if parameter is a RGB image.
mat2gray
Converts a matrix to a intensity image.
rgb2gray
Converts an RGB image to a gray scale image, or a color map to a gray map.
rgb2ind
Convert and RGB image to an Octave indexed image.
label2rgb
Converts a labeled image to an RGB image.

Colour maps

flag
Create color colormap.
lines
Not implemented.
colorcube
Not implemented.
vga
Not implemented.
contrast
Return a gray colormap that maximizes the contrast in an image.
colorgradient
Define a colour map which smoothly traverses the given colors.

Region-based and block processing

roicolor
Select a Region Of Interest of an image based on color.
roifill
Not implemented.
roifilt2
Not implemented.
roipoly
Not implemented.
poly2mask
Convert a polygon to a region mask.
bestblk
Calculates the best size of block for block processing.
blkproc
Processes image in blocks using user-supplied function.
nlfilter
Processes image in sliding blocks using user-supplied function.
im2col
Rearranges image blocks into columns.
col2im
Rearranges matrix columns into blocks.