在Matlab中转换数据类型的有效方法(double与im2double) [英] The efficient way to convert datatype in Matlab (double vs. im2double)

问题描述

我想将truecolor图像转换为双精度，据我所知有两种方法可以做到:

I want to convert a truecolor image to double precision, and as far as I know there are two ways to do that:

1. double(rgb_img);
2. im2double(rgb_img);

哪个效率更高?

谢谢！

推荐答案

下面是一个基准测试代码，用于将 double 与 im2double 进行比较，即使它们不一定产生相同的结果其他解决方案中说明的结果-

Here's a benchmarking code to compare double against im2double even though they don't necessarily produce the same results as explained in the other solution(s) -

N_arr = [100 200 500 1000 2000 4000]; %// datasize array
timeall = zeros(4,numel(N_arr));
for k1 = 1:numel(N_arr)

    rgb_img = uint8(randi([0 255],N_arr(k1))); %// Input to functions

    f = @() double(rgb_img);
    timeall(1,k1) = timeit(f);
    clear f

    f = @() im2double(rgb_img);
    timeall(2,k1) = timeit(f);
    clear f
end
figure,hold on,grid on
plot(N_arr,timeall(1,:),'-ro'),plot(N_arr,timeall(2,:),'-kx')
legend('DOUBLE','IM2DOUBLE'),
xlabel('Datasize ->'),ylabel('Time(sec) ->')

结果-

现在，这是有道理的，因为在内部 im2double 调用 double.

Now, this makes sense because internally im2double calls double.

现在，假设您要处理 uint8 图像，要具有与 double 相同的功能，则需要在以后缩小比例.因此，您需要相应地编辑功能句柄-

Now, assuming you are dealing with uint8 images, to have the same functionality with double, you need to scale it down afterwards. So you need to edit the function handle accordingly -

f = @() double(rgb_img)./255;

当时的情节结果是-

所以，现在看来差别不大.

So, apparently not much of a difference now.

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