The Image object for image operations and processing

The Image class is a core component of this Toolbox. It encapsulates a NumPy array that contains the pixel values of a greyscale or color image as a 2D or 3D array respectively. An Image instance has a very large number of methods that perform useful operations on an image and wrap low-level operations performed using NumPy or OpenCV.

Image attributes and datatype

Image attributes

Describe the attributes of an Image.

width	Image width
height	Image height
size	Image size
npixels	Number of pixels in image plane
name	Set/get image name
centre	Coordinate of centre pixel
centre_int	Coordinate of centre pixel as integer
center	Coordinate of center pixel
center_int	Coordinate of centre pixel as integer
__str__	Single line summary of image parameters
__repr__	Single line summary of image parameters

Predicates

Test attributes of an Image.

isfloat	Image has floating point pixel values?
isint	Image has integer values?
isbool	Image has bolean values?
iscolor	Image has color pixels?
isbgr	Image has BGR color order?
isrgb	Image has RGB color order?

Image coordinates

Describe the pixel coordinates of an Image.

umax	Image maximum u-coordinate
vmax	Image maximum v-coordinate
uspan	Linear span of image horizontally
vspan	Linear span of image vertically
meshgrid	Coordinate arrays for image
contains	Test if coordinate lies within image

NumPy pixel data

Return Image pixel data as a NumPy array.

A	Set/get the NumPy array containing pixel values
rgb	Image as NumPy array in RGB color order
bgr	Image as NumPy array in BGR color order
image	Image as NumPy array
to_int	Image as integer NumPy array
to_float	Image as float NumPy array
view1d	Convert image to a column view
shape	Image shape
ndim	Number of image array dimensions

Image datatype

Describe or change the datatype of Image pixel values.

isfloat	Image has floating point pixel values?
isint	Image has integer values?
isbool	Image has bolean values?
dtype	Datatype of image
to	Convert image datatype
astype	Cast image datatype
to_int	Image as integer NumPy array
to_float	Image as float NumPy array
cast	Cast value to same type as image
like	Convert value to the same type as image
minval	Minimum value of image datatype
maxval	Maximum value of image datatype
true	True value for logical image
false	False value for logical image

Image processing

Sub images

Extract sub-images or planes from an Image instance.

roi	Extract region of interest
plane	Extract plane(s) from color image
red	Extract the red plane of a color image
green	Extract the green plane of a color image
blue	Extract the blue plane of a color image
__getitem__	Return pixel value or slice from image

Color info

Return information about the color planes of an Image instance.

iscolor	Image has color pixels?
isbgr	Image has BGR color order?
isrgb	Image has RGB color order?
colororder	Set/get color order of image
colororder_str	Image color order as a string
colordict	Parse a color order specification
nplanes	Number of color planes
plane	Extract plane(s) from color image

Color space and gamma

Convert between color spaces and perform gamma encoding and decoding.

mono	Convert color image to monochrome
colorize	Colorize a greyscale image
chromaticity	Create chromaticity image
colorspace	Transform a color image between color representations
gamma_encode	Gamma encoding
gamma_decode	Gamma decoding
kmeans_color	k-means color clustering

Composition

Combine multiple Image instances into a single Image instance.

Hstack	Horizontal concatenation of images
Vstack	Vertical concatenation of images
Tile	Tile images into a grid
Overlay	Overlay two greyscale images in different colors

Monadic functions

Operate elementwise on an Image instance and returns a new Image instance.

abs	Absolute value of image
sqrt	Square root of image
LUT	Apply lookup table
apply	Apply a function to an image
clip	Clip pixel values
normhist	Histogram normalisaton
stretch	Image normalisation
threshold	Image threshold
threshold_interactive	Interactive thresholding
threshold_adaptive	Adaptive threshold
invert	Invert image

Dyadic functions

Operate elementwise on two Image instances and return a new Image instance.

apply2	Apply a function to two images
blend	Image blending
choose	Pixel-wise image merge
paste	Paste an image into an image
direction	Gradient direction

Linear filtering

Linear filtering operations including convolution, corner and edge detection.

convolve	Image convolution
smooth	Smooth image
gradients	Compute horizontal and vertical gradients
direction	Gradient direction
Harris_corner_strength	Harris corner strength image
scalespace	Compute image scalespace sequence
pyramid	Pyramidal image decomposition
canny	Canny edge detection

Non-linear (morphological) filtering

Variety of non-linear morphological operations.

window	Generalized spatial operator
zerocross	Compute zero crossing
rank	Rank filter
medianfilter	Median filter
distance_transform	Distance transform
erode	Morphological erosion
dilate	Morphological dilation
close	Morphological closing
open	Morphological opening
morph	Morphological neighbourhood processing
hitormiss	Hit or miss transform
thin	Morphological skeletonization
thin_animate	Morphological skeletonization with animation
endpoint	Find end points on a binary skeleton image
triplepoint	Find triple points

Image labeling

Binary, greyscale and color image segmentation using various algorithms.

labels_binary	Blob labelling
labels_MSER	Blob labelling using MSER
labels_graphseg	Blob labelling using graph-based segmentation
kmeans_color	k-means color clustering

Image similarity

Various scalar image similarity measures.

sad	Sum of absolute differences
ssd	Sum of squared differences
ncc	Normalised cross correlation
zsad	Zero-mean sum of absolute differences
zssd	Zero-mean sum of squared differences
zncc	Zero-mean normalized cross correlation
similarity	Locate template in image

Shape changing

Changing the shape of an Image instance.

trim	Trim pixels from the edges of the image
pad	Pad the edges of the image
decimate	Decimate an image
replicate	Replicate image pixels
roi	Extract region of interest
samesize	Automatic image trimming
scale	Scale an image
view1d	Convert image to a column view

Image distortion

Distorting the image within an Image instance.

roll	Roll image by row or column
rotate	Rotate an image
rotate_spherical	Rotate a spherical image
warp	Image warping
warp_affine	Affine warp of image
warp_perspective	Perspective warp
interp2d	Image warping
undistort	Undistort image

Multiview operations

Stereo image processing, rectification, and display.

stdisp	Interactive display of stereo image pair
stereo_simple	Simple stereo matching
DSI_refine	Refine disparity from disparity space image
stereo_BM	Stereo block matching
stereo_SGBM	Stereo semi-global block matching
rectify_homographies	Create rectification homographies

Binary operators

Arithmetic and logical operations can be performed elementwise on: Image ☆ Image, Image ☆ scalar, scalar ☆ Image. The result is always an Image.

__add__	Overloaded + operator
__sub__	Overloaded - operator
__mul__	Overloaded * operator
__pow__	Overloaded ** operator
__sub__	Overloaded - operator
__truediv__	Overloaded / operator
__floordiv__	Overloaded // operator
__and__	Overloaded & operator
__or__	Overloaded | operator
__xor__	Overloaded ^ operator
__lshift__	Overloaded << operator
__rshift__	Overloaded >> operator
__eq__	Overloaded == operator
__ne__	Overloaded != operator
__gt__	Overloaded > operator
__ge__	Overloaded >= operator
__lt__	Overloaded < operator
__le__	Overloaded <= operator

Unary operators

Operations can be performed elementwise on an Image and the result is always an Image.

__minus__	Overloaded unary - operator
__invert__	Overloaded ~ operator

Image feature extraction

Whole image features

Histograms

hist	Image histogram

Statistical measures

mean	Mean value of all pixels
std	Standard deviation of all pixels
var	Variance of all pixels
median	Median value of all pixels
stats	Display pixel value statistics

Image moments

mpq	Image moments
npq	Normalized central image moments
upq	Central image moments
moments	Image moments
humoments	Hu image moment invariants

Other

sum	Sum of all pixels
nonzero	Find non-zero pixel values as 2D coordinates
flatnonzero	Find non-zero pixel values as 1D indices
peak2d	Find local maxima in image
otsu	Otsu threshold selection

Region features

Find homogeneous regions, text or fiducual tags.

blobs	Find and describe blobs in image
MSER	Find MSER features in image
ocr	Optical character recognition
fiducial	Find fiducial markers in image

Line features

Find lines in an image.

canny	Canny edge detection
Hough	Find Hough line features

Point/corner features

Find distincitive points in an image.

SIFT	Find SIFT features in image
ORB	Find ORB features in image
BRISK	Find BRISK features in image
AKAZE	Find AKAZE features in image
Harris	Find Harris features in image
ComboFeature	Combination feature detector and descriptor

Image i/o

File

Read	Read image from file
write	Write image to file
metadata	Get image EXIF metadata

Graphical

disp	Display image
showpixels	Display image with pixel values
anaglyph	Convert stereo images to an anaglyph image
stdisp	Interactive display of stereo image pair

Text

String	Create a small image from text string
print	Print image pixels in compact format
strhcat	Format several small images concatenated horizontally

Constant images

Create images that are constant, random, or have a simple geometric pattern.

Zeros	Create image with zero value pixels
Constant	Create image with all pixels having same value
String	Create a small image from text string
Random	Create image with random pixel values
Squares	Create image containing grid of squares
Circles	Create image containing grid of circles
Ramp	Create image of linear ramps
Sin	Create image of sinusoidal intensity pattern

Graphical annotation

Render simple graphical annotations into an image.

draw_line	Draw line into image
draw_circle	Draw circle into image
draw_box	Draw box into image

Test images

Sometimes it helpful to create, process and numerically display small example images. These functions can help with that

String	Create a small image from text string
print	Print image pixels in compact format
strhcat	Format several small images concatenated horizontally
showpixels	Display image with pixel values