如何在 Matlab 中找到并突出显示图像中最亮的区域？

Question

亲爱的，

恳请您给予支持。我的目标是找到 RGB 图像的最亮区域并在不使用其他工具的情况下突出显示它。请看下面我的例子。

rgbImage = imread( 'Zoom1_WhiteImage.png' );
imshow(rgbImage);

[rows, columns, numberOfColorChannels] = size(rgbImage)

[x, y] = meshgrid(1:columns, 1:rows);
% Extract the individual red, green, and blue color channels.
% Need to cast to double or else x and y will be clipped to 255 when we concatenate them.
if numberOfColorChannels == 1
    % Leave as gray scale.
    % Get array listing [r, g, b, x, y].  Using (:) will turn all the 2-D arrays into column vectors.
    output = [rgbImage(:), x(:), y(:)];
else
    redChannel = double(rgbImage(:, :, 1));
    greenChannel = double(rgbImage(:, :, 2));
    blueChannel = double(rgbImage(:, :, 3));
    % Get array listing [r, g, b, x, y].  Using (:) will turn all the 2-D arrays into column vectors.
    output = [redChannel(:), greenChannel(:), blueChannel(:), x(:), y(:)];
end

[rows, columns] = find(rgbImage == 155);
imshow(rgbImage);
hold on

不幸的是，我正在为如何继续绘制应该覆盖灰色图像的点而苦恼。

你能帮我完成代码吗？

Answer 1

我建议您阅读 MATLAB 中的逻辑索引 - 这是一个非常强大的概念，它允许您通过展平数组和创建单独的索引数组来跳过您尝试做的大部分事情meshgrid。 Here is an article 例如，解决底部的逻辑索引问题。

我已经修改并添加到您的代码中，因此它使用逻辑索引来完成工作。我在 R2019b 中对此进行了测试。

rgbImage = imread( 'Zoom1_WhiteImage.png' );
imshow(rgbImage);

[rows, columns, numberOfColorChannels] = size(rgbImage)

% This is unnecessary - the 'find' command will generate the indices 
%   without you preparing a matrix of them:
% [x, y] = meshgrid(1:columns, 1:rows);   

if numberOfColorChannels == 1
    % No need to flatten the image, or combine it with indices:
    %output = [rgbImage(:), x(:), y(:)];

    brightness = rgbImage;  % For a 1 channel image, brightness is the same as the original pixel value.

else
%     redChannel = double(rgbImage(:, :, 1));
%     greenChannel = double(rgbImage(:, :, 2));
%     blueChannel = double(rgbImage(:, :, 3));
    % Get array listing [r, g, b, x, y].  Using (:) will turn all the 2-D arrays into column vectors.
%     output = [redChannel(:), greenChannel(:), blueChannel(:), x(:), y(:)];

    % For an RGB image, the brightness can be estimated in various ways, here's one standard formula: 
    brightness = (0.2126*rgbImage(:, :, 1) + 0.7152*rgbImage(:, :, 2) + 0.0722*rgbImage(:, :, 3));
end

% Establish a brightness threshold - pixels brighter than this value will
% be highlighted
threshold = 215;

% Create a zero-filled mask of equal size to the image to hold the
% information of which pixels met the brightness criterion:
mask = zeros(rows, columns, 'logical');

% Assign "1" to any mask pixels whose corresponding image pixel met the
% brightness criterion:
mask(brightness > threshold) = 1;

figure;
% Overlay and display mask. imoverlay was introduced in R2017, but the 
% syntax has changed a bit, so check the version you're using. You can also
% use imfuse, or imshowpair, or make your own image blending algorithm, 
% depending on how you want it to look.
imshow(imoverlay(rgbImage, mask, 'red'));
hold on

如何在 Matlab 中找到并突出显示图像中最亮的区域？

How to find and highlight the brightest region an image in Matlab?

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grayscale