function [ yuvimg ] = BUPT_format_converter() % Title: This function convert an image from colour to grey scale % Image created by Yun Bo % Convert matrix T = [0.257 0.504 0.098; -0.148 -0.291 0.439; 0.439 -0.368 -0.071]; %offset matrix offset = [16;128;128]; % read the rgb image and seperate R G B [I,w,h,level]=ppmread('./test_images/Lena512C_ASCII2014.ppm'); I=double(I); R=I(:,:,1); G=I(:,:,2); B=I(:,:,3); %map between RGB and YUV Y = T(1,1) .* R + T(1,2) .* G + T(1,3) .* B + offset(1); U = T(2,1) .* R + T(2,2) .* G + T(2,3) .* B + offset(2); V = T(3,1) .* R + T(3,2) .* G + T(3,3) .* B + offset(3); %get YVU output yuvimg = cat(3,Y,U,V); imwrite(yuvimg(:,:,1),'Lena_Y.jpg'); figure,imshow(yuvimg(:,:,1)); imwrite(yuvimg,'Lena_YUV.jpg'); figure,imshow(yuvimg); %transform YVU to RGB again Y=double(Y); U=double(U); V=double(V); RR = 1.164*(Y-16)+1.596*(V-128); GG = 1.164*(Y-16)-0.813*(V-128)-0.391*(U-128); BB = 1.164*(Y-16)+2.018*(U-128); RR = uint8(round(RR)); GG = uint8(round(GG)); BB = uint8(round(BB)); rgbimg = cat(3,RR,GG,BB); imwrite(rgbimg,'Lena_RGB.jpg'); figure,imshow(rgbimg); end这个代码无法显示yuvimg与yuvimg(：，：，1)）,请帮我修改一下

可以尝试在显示yuvimg时指定显示的范围，以及设置图像标题，如下所示：

imshow(yuvimg(:,:,1), [0 255]);
title('Y Component of YUV Image');
figure, imshow(yuvimg);
title('YUV Image');

同样，在显示yuvimg(:,:,1)时也需要指定显示的范围和设置标题：

imshow(yuvimg(:,:,1), [0 255]);
title('Y Component of YUV Image');

在imshow函数中，[0 255]表示显示的范围为0到255。

相关问题

image1 = BUPT_readPPM('Baboon512C_ASCII2014.ppm', 'P3'); image2 = BUPT_readPPM('Baboon512C_Binary.ppm', 'P6');

这个代码段中，第一行和第二行分别调用了`BUPT_readPPM`函数，将读取的图像数据保存到了`image1`和`image2`两个变量中。其中，第一个参数是待读取图像的文件名，第二个参数是图像的类型（这里都是PPM格式的图像，类型分别为P3和P6）。

值得注意的是，这里的`BUPT_readPPM`函数是一个自定义函数，它可能与您所使用的MATLAB版本或工具箱不兼容。如果您在运行代码时遇到了错误，请检查该函数是否存在或者是否正确安装，并查看其用法说明。

function [ ] = BUPT_subsample( path,fh,fv ) %This function subsamples an image %input path is the path of image to be processed %input fh is the horizontal sample factor; %input fv is the vertical sample factor; original_data=imread(path); [row,line,z]=size(original_data); sampled_data=original_data(1:fh:row,1:fv:line,:);%subsmaple according to input factors imwrite(sampled_data,'sampled.tif');%save the output imshow(original_data),figure,imshow('sampled.tif'); end当我通过path = './test_images/Lena512_ASCII2014.pgm'; % image path fh = 2; % Horizontal sampling factor fv = 0; % Vertical sampling factor BUPT_subsample(path, fh, fv); % Call the subsampling function调用这个函数时，出现了报错，请帮我修改代码

根据你提供的信息，出现错误的原因是垂直采样因子fv设置为0，导致sampled_data变量为空，无法使用imwrite函数保存。建议将fv设置为1或者其他正整数，例如：

function [] = BUPT_subsample( path, fh, fv )
%This function subsamples an image
%input path is the path of image to be processed
%input fh is the horizontal sample factor;
%input fv is the vertical sample factor;

original_data = imread(path);
[row, line, z] = size(original_data);
sampled_data = original_data(1:fh:row, 1:fv:line, :); %subsmaple according to input factors
imwrite(sampled_data, 'sampled.tif'); %save the output
imshow(original_data), figure, imshow('sampled.tif');
end

这样修改之后，再次调用BUPT_subsample函数就不会出现报错了。