rgb2gray
Convert RGB image or colormap to grayscale
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Syntax
I = rgb2gray(RGB)
newmap = rgb2gray(map)
gpuarrayB = rgb2gray(gpuarrayA)
Description
I = rgb2gray(RGB) converts the truecolor image RGB to the grayscale intensity image
I. rgb2gray converts RGB images to grayscale by eliminating the hue and saturation information while retaining
the luminance.
newmap = rgb2gray(map) returns a grayscale colormap equivalent to map.
gpuarrayB = rgb2gray(gpuarrayA) performs the operation on a GPU. gpuarrayA can be either
an RGB image or a colormap. gpuarrayB is a gpuArray of the same type as gpuarrayA. This syntax requires
the Parallel Computing Toolbox™
Note: A grayscale image is also called a gray-scale, gray scale, or gray-level image.
Class Support
If I is an RGB image, it can be of class uint8, uint16, single, or double. The output image I is of the
same class as the input image. If I is a colormap, the input and output colormaps are both of class double.
If gpuarrayA is an RGB gpuArray image, it can be uint8, uint16, single, or double. The output
gpuArray imagegpuarrayB has the same class as the input image. If gpuarrayA is a colormap, the input and
output colormaps are gpuArrays of class double.
Examples
Convert an RGB image to a grayscale image.
I = imread('board.tif');
J = rgb2gray(I);
figure, imshow(I), figure, imshow(J);
Convert an RGB image to a grayscale image on a GPU.
I = gpuArray(imread('board.tif'));
J = rgb2gray(I);
figure, imshow(I), figure, imshow(J);
Convert the colormap to a grayscale colormap.
[X,map] = imread('trees.tif');
gmap = rgb2gray(map);
figure, imshow(X,map), figure, imshow(X,gmap);
