Then use that value as a row index into the colormap matrix, map: s.map(61,:) To get the color of the (5,5) pixel, first see what X(5,5) is: s.X(5,5) X contains the pixel values, and map contains the associated colormap. The X and map variables stored in clown.mat are both necessary to display the image correctly. This form returns % a structure whose fields are the variables stored % in the MAT-file. s = load( 'clown') % This the functional form of load. As an example, let's use an indexed image that ships with MATLAB, clown.mat ( Ned's favorite). If the image CData is two-dimensional, then the CData values are treated as lookup indices into the axes or the figure colormap. Title( 'Changing the figure colormap does not affect the pixel colors') With truecolor images, changing the colormap has no effect on the image colors displayed.
For example, if we lower the green value of the pixel in the first row, second column from 1.0 to 0.5, we make a darker shade of green. We can change the values in this property directly to change the image colors. We'll come back to it in one of the next couple of blog posts.)ĬData, which stands for color data, contains the 2-by-3-by-3 array we created above. (I won't be talking further about CDataMapping today. The object display shows the most commonly used properties of the image object, CData and CDataMapping. Now let's peek at the Graphics image object, which was returned above by the call to imshow: im This type of image, in which each pixel color is represented by three values, is often called a truecolor image. The yellow color is a mix of no red light, full-intensity green light, and full-intensity blue light. Similarly, here are the three values for the yellow pixel: rgb(2,3,:) So the magenta color above is a mix of full-intensity red light, no green light, and full-intensity blue light. The value 1 corresponds to full-intensity light, whereas the value 0 corresponds to no light. The three numbers represent an additive mix of red, green and blue light. Here are the three values for the magenta color, which is row 2, column 2: rgb(2,2,:) That's because we are using 3 different values to specify a pixel color. The size of rgb along the third dimension is 3. The first two numbers in the size of rgb tell you the number of rows and columns of pixels. So, what's going on here? Look first at the size of rgb: size(rgb) Title( 'Truecolor image with six pixels') Im = imshow(rgb, 'InitialMagnification', 'fit') I'll start by constructing a simple image containing just six pixels: red, green, blue, cyan, magenta, and yellow.
0 kommentar(er)
