Question

在这段代码中，我有一个包含10个类的聚类图像，我想为每个级别提取10个不同的图像并保存为10个图像下面是代码，我使用

tic
numberOfClasses = 10;
segment_label_images = cell(1,numberOfClasses);
pixelCount = zeros(1,numberOfClasses);
[rs, cs] = size(classImage);
% classImage has intensity range from 1-numberOfClasses
for k = 1:numberOfClasses
    for i = 1:rs
        for j = 1:cs
            if classImage(i,j) == k
                segment_label_images{k}(i,j) = 1;
            else
                segment_label_images{k}(i,j) = 0;
            end
        end
    end
pixelCount(k) = sum(segment_label_images{k}(:));
%figure, imshow(segment_label_images{k},[]);
end
toc

在这里，我有3个for循环，我认为这会影响计算时间。经过的时间是0.089413秒。

任何避免循环以改善补偿时间的建议。谢谢，Gopi

Answer 1

假设for k = 1:numberOfClasses segment_label_images{k} = classImage == k; pixelCount(k) = sum(segment_label_images{k}(:)); end是一个矩阵，你可以用

加快速度

[{"eventId":"1","eventName":"INSERT","eventVersion":"1.0","eventSource":"aws:dynamodb","awsRegion":"us-west-2","image":{"Message":"New item!","Id":101}},{"eventId":"2","eventName":"MODIFY","eventVersion":"1.0","eventSource":"aws:dynamodb","awsRegion":"us-west-2","image":{"Message":"This item has changed","Id":101}},{"eventId":"3","eventName":"REMOVE","eventVersion":"1.0","eventSource":"aws:dynamodb","awsRegion":"us-west-2","image":{"Message":"This item has changed","Id":101}}]

Answer 2

假设MATLAB 2016b（或Octave）：

k = permute(1:numberOfClasses, [1,3,2]);
segment_label_images = (classImage == k);
pixelCount = squeeze(sum(sum(segment_label_images, 1), 2));

对于2016b之前的MATLAB，只需添加bsxfun：

k = permute(1:numberOfClasses, [1,3,2]);
segment_label_images = bsxfun(@eq, classImage, k);
pixelCount = squeeze(sum(sum(segment_label_images, 1), 2));

当然，这两个都将segment_label_images作为3D数组而不是单元格数组。鉴于所有阵列都是相同的大小，我更喜欢使用多维数组而不是单元数组，以提高速度和方便性。当然，如果需要，它可以转换为单元格数组。

如何避免此代码中的for循环以缩短计算时间

2 个答案: