Question

我正试图找到R，G＆amp;的中位数值。每个像素的B通道为每组10个图像中的一个100，以找到背景图像。我的价值观似乎都是正确的，但当我尝试在代码末尾显示背景时，它总是白色的，请帮助

%// list all the files in some folder
folder = '~/V&R/1/';
filelist = dir(folder);
images = zeros(480,640,3,100);
% images = [];
%// the first two in filelist are . and ..

count = 1;
for i=3:size(filelist,1)

    if filelist(i).isdir ~= true
        fname = filelist(i).name;
        %// if file extension is jpg
        if strcmp( fname(size(fname,2)-3:size(fname,2)) ,'.jpg'  ) == 1
            tmp = imread([folder fname]);
            images(:,:,:,count) = tmp;
            count = count +1;

        end
    end
end


background = zeros(480,640,3);
 for j=1:480
    for i=1:640
        tmpR = zeros(1,10);
        tmpG = zeros(1,10);
        tmpB = zeros(1,10);
        for k=1:10
            tmpR(k) = images(j,i,1,k*10);
            tmpG(k) = images(j,i,2,k*10);
            tmpB(k) = images(j,i,3,k*10);

        end
        background(j,i,1) = floor(median(tmpR));
        background(j,i,2) = floor(median(tmpG));
        background(j,i,3) = floor(median(tmpB));
    end
 end
imshow(background)

感谢

Answer 1

第一步是对代码进行矢量化。而不是以下代码块：

background = zeros(480,640,3);
for j=1:480
  for i=1:640
    tmpR = zeros(1,10);
    tmpG = zeros(1,10);
    tmpB = zeros(1,10);
    for k=1:10
        tmpR(k) = images(j,i,1,k*10);
        tmpG(k) = images(j,i,2,k*10);
        tmpB(k) = images(j,i,3,k*10);

    end
    background(j,i,1) = floor(median(tmpR));
    background(j,i,2) = floor(median(tmpG));
    background(j,i,3) = floor(median(tmpB));
  end
end

写：

subimages = images(:, :, :, 1:10:end);
background = median(subimages, 4);

现在如前所述，使用imshow和[]选项来显示你的图像：

imshow(background, []);

如果您仍然看到白色图像，那么您可能正在处理不在[0,1]之间的双值矩阵。 Matlab中的图像通常是类double或单个，值介于0和1之间，或者类uint8或uint16，其值分别为0,255或0,65535。如果您的值介于0和255之间但类（子图像）返回double或single，请在使用imshow（）之前执行以下操作：

subimages = uint8(subimages);

Answer 2

尝试

imshow(background,[])

使用imshow时，MATLAB需要设置显示范围。对于单灰度或双灰度图像，默认显示范围为[0 1]。这意味着任何大于1的值都将表示为白色。您可以通过手动设置自己的显示范围来解决此问题，例如

imshow(background,[0 100],

或者您可以让MATLAB通过

计算新的显示范围

imshow(background,[])

与

相同

imshow(background,[min(background(:)) max(background(:))])

Answer 3

您可以将代码重写为：

%# get filenames of all JPG images in some folder
folder = '~/V&R/1/';
filelist = dir( fullfile(folder,'*.jpg') );
filelist = strcat(folder, filesep, {filelist.name});

%# read files, and store as 'double' images in a 4D matrix
images = zeros(480,640,3, numel(filelist), 'double');
for i=1:numel(filelist)
    images(:,:,:,i) = im2double( imread(filelist{i}) );
end

%# estimate background using median
subimages = images(:,:,:,1:10:end);
background = median(subimages, 4);
imshow(background)

Matlab - 显示背景图像

3 个答案: