In an RGB array of class double , each color component is a value between 0 and 1. The color components of an 8-bit RGB image are integers in the range [0, ] rather than floating-point values in the range [0, 1]. The truecolor images analyzed are m -by- n -by-3 arrays of uint8.
Each of the three-color components is a matrix that is decomposed using the 2-D wavelet decomposition scheme. Wavelet Toolbox software lets you work with some other types of images. Using the imread function, the various tools using images try to load indexed images from files that are not MAT files for example, PCX files. Use the imfinfo function to find the type of image stored in the file. If the file does not contain an indexed image, the load operation fails.
The color bar to the right of the image is not smooth and does not monotonically progress from dark to light. This type of indexed image is not suitable for direct wavelet decomposition with the toolbox and needs to be preprocessed.
Next, convert the RGB matrices into a gray-scale intensity image, using the standard perceptual weightings for the three-color components:. Then, convert the gray-scale intensity image back to a gray-scale indexed image with 64 distinct levels and create a new colormap with 64 levels of gray:. The color bar of the converted image is now linear and has a smooth transition from dark to light.
The image is now suitable for wavelet decomposition. Finally, save the converted image in a form compatible with the Wavelet Toolbox Wavelet Analyzer app:. Suppose the file myImage. Use the following commands to convert this image:. Search for:. For example: returns the value of the pixel at row 2 and column 15 of the image I. Indexed Images A typical color image requires two matrices: a colormap and an image matrix.
Each row of the colormap matrix is a 1-by-3 red, green, blue RGB color vector that specifies the intensity of the red, green, and blue components of that color. Wavelet Decomposition of Indexed Images Indexed images can be thought of as scaled intensity images, with matrix elements containing only integers from 1 to n , where n is the number of discrete shades in the image.
How Decompositions Are Displayed Note that the coefficients, approximations, and details produced by wavelet decomposition are not indexed image matrices. To display these images in a suitable way, the Wavelet Analyzer app follows these rules: Reconstructed approximations are displayed using the colormap map.
Wavelet Matlab Pdf Example The color components of an 8-bit RGB image are integers in the range [0, ] rather than floating-point values in the range [0, 1]. Other Images Wavelet Toolbox software lets you work with some other types of images. Example 1: Converting Color Indexed Images Name Size Bytes Class X2 x double array map 64x3 double array The color bar to the right of the image is not smooth and does not monotonically progress from dark to light.
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