如何在MatLab中打开原始的YCbCr图像文件？

Question

I am trying to open a 1920x1080 YCbCr raw image file in Matlab, however I am having difficulties getting the following code below to work:

fid = fopen(filePath);
image = fread(fid, 1920*1080, 'uint8=>uint8');
fclose(fid); 
image = reshape(image, 1080, 1920);

However, when I go to show the image, it does not look as expected.

The actual image should be colour, however I get a strange black and white image, not resembling the expected output at all.

I have also tried loading it into a 3D array, with each dimension representing one of the Y, Cb and Cr channels, however this also produced a similar output as described before.

Any help would be appreciated.

Answer 1

Ignore this bit and look below at the EDIT:

I don't understand why you are using fread ? Why not use imread , which is mean't for reading images? Using this infamous original image , as a base for my test script, I could display a YCbCr image, as shown in the little script below.

 original = imread("lenna.jpg"); % figure, imshow(original); % if you want to see how the original image looks YCbCr_version = rgb2ycbcr(original); % figure, imshow(YCbCr_version); % if you want to see how the YCbCr image looks imwrite(YCbCr_version, "out.jpg"); YCbCr_fromFile = imread("out.jpg"); figure, imshow(YCbCr_fromFile); 

EDIT:

• IF however you have a binary version of the file and can only read it using using fread ,

then the following script should work,

clc;
clear;
close all;

original = imread("lenna.jpg");
% figure, imshow(original); % if you want to see how the original image looks
YCbCr_version = rgb2ycbcr(original);
% figure, imshow(YCbCr_version);  % if you want to see how the YCbCr image looks

fileID = fopen('out.bin','w');
fwrite(fileID, YCbCr_version, 'uint8');
fclose(fileID);

fileID = fopen('out.bin','r');
fromFile = fread(fileID, 512*600*3, 'uint8=>uint8');
fclose(fileID);
image = reshape(fromFile, 512, 600, 3);
imagesc(image)

The point is, in the read operation, you have to give the 3 channels in the multiplier also, as color images have this 3rd dimension, ie 512*600*3 . If you only give 512*600 , as you were doing, you would have no color info. Also the reshape function would need to be changed to take into account the 3rd dimension. Hence, reshape(fromFile, 512,600, 3) .

• YCbCr version loaded from the file

Answer 2

As you said "Any help would be appreciated" , I thought I would mention you can simply convert a raw YCbCr file to PNG, TIFF, JPEG or any other format file with ImageMagick which is installed on most Linux distros and is available for macOS and Windows.

Start a Terminal, (or Command Prompt if under Windows), and convert the YCbCr image.raw to PNG with:

magick -size 1920x1080 -depth 8  YCbCr:image.raw  result.png

Or, say a CCIR 601 YUV file to NetPBM PPM format:

magick -size 800x600 -depth 8 YUV:image.raw result.ppm