MATLAB VIDEO AND IMAGE PROCESSING BLOCKSET 3 User's Guide download pdf (Page 215)

Pixel Statistics

Video and Image Processing Blockset contains blocks that can provide

information ab ou t the data values that make up an im age. Blocks f rom the

Statistics library, such as the 2-D Maximum and 2-D Autocorrelation blocks,

can help you determine this information.

This section includes the following topic:

• “Finding the Histogram of an Image” on page 7-59 — Use the 2-D Histogram

block to calculate the histogram of the R, G, and B values in an image

Finding the Histogram of an Image

The 2-D Histogram block computes the frequency distribution of the elements

in each input image by sorting the elements into a specified number of

discrete bins. You can u se the 2-D Histogram block to calculate the histogram

of th e R, G, and/or B va lues in an image. This example shows you how to

accomplish this task:

1 DefineanRGBimageintheMATLABworkspace. ToreadinanRGB

image from a PNG file, at the MATLAB command prompt, type

I= im2double(imread('peppers.png'));

I is a 486-by-732-by-3 array of double-precision floating-point values.

Each plane of the array represents the red, green, or blue color values

of the image.

2 To view the image this matrix represents, at the MATLAB command

prompt, type

imshow(I)

7-59

1 2 ... 210 211 212 213 214 215 216 217 218 219 220 ... 251 252

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MATLAB VIDEO AND IMAGE PROCESSING BLOCKSET 3 User's Guide Page 215