我有一个RGB图像。因此,当我在Matlab中进行[image2, map] = imread('image.png')
时,得到的地图[]
符合预期。我想将该RGB图像转换为索引图像。我想将其另存为一个通道的索引图像,并看到here之类的颜色。
引用here我在Matlab中使用了以下代码。
image2 = imread('image.png');
IND = rgb2ind(image2,256);
imwrite(IND, 'imageIndexed.png')
但是保存的是灰度图像。当我读回它时,地图仍然是[]
。我要编写它,使其成为彩色图像,并且下次使用[image2, map] = imread('image.png')
时,地图将不会变为[]
。有人可以帮忙吗?
答案 0 :(得分:2)
您可以执行以下操作:
将图像从RGB转换为2种颜色的索引图像:
[X, cmap] = rgb2ind(RGB, 2);
将彩色图的索引替换为黑白:
cmap(1, 1:3) = [0, 0, 0]; %Fist color is black
cmap(2, 1:3) = [1, 1, 1]; %Second color is white
将索引图像(和地图)写入PNG文件:
imwrite(X, cmap, 'K.png');
注意:将图像和索引图像写入文件时,需要写入矩阵和颜色图。
从PNG文件读取图像(和地图),并将其转换为RGB图像:
[I, cmap2] = imread('K.png');
L = ind2rgb(I, cmap2);
这是一个代码示例:
RGB = imresize(imread('peppers.png'), 0.5); %Read input RGB image.
%Convert image to indexed image with 2 color.
[X, cmap] = rgb2ind(RGB, 2);
J = ind2rgb(X, cmap);
%Replace indices of color map:
cmap(1, 1:3) = [0, 0, 0]; %Fist color is black
cmap(2, 1:3) = [1, 1, 1]; %Second color is white
K = ind2rgb(X, cmap);
figure;imshow(RGB);
figure;imshow(J);
figure;imshow(K);
imwrite(X, cmap, 'K.png');
[I, cmap2] = imread('K.png');
L = ind2rgb(I, cmap2);
figure;imshow(L);
为完成操作,下面是使用您的reference的示例:
[webX, web_cmap] = imread('https://i.stack.imgur.com/zuIra.png'); %Read input image and color map.
RGB = ind2rgb(webX, web_cmap);
%Convert image to indexed image with 4 colors.
[X, cmap] = rgb2ind(RGB, 4);
%Collect histogram
H = histogram(X, 4);
H = H.Values';
%Replace indices of color map: set the color with minimal pixels to white, and other to black.
cmap(H == min(H), :) = 1; %Fist color is black
cmap(H ~= min(H), :) = 0; %Set other three colors to black
%Convert to RGB
bwRGB = ind2rgb(X, cmap);
%Convert to indexed image with only 2 colors:
[X, cmap] = rgb2ind(bwRGB, 2);
imwrite(X, cmap, 'K.png');
[I, cmap2] = imread('K.png');
L = ind2rgb(I, cmap2);
figure;imshow(L);