Problem on gray scale image.
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Hi. i used gray = rgb2gray(I) at command window but why can't i get a grayscale image? thank you!
回答（2 个）
Walter Roberson
2012-9-19
grayscaleimage = rgb2gray(I);
image(grayscaleimage);
colormap(gray);
Please note that "gray" is a MATLAB function for constructing grayscale colormaps. Writing to a variable named "gray" interferes with using the function "gray".
Esther
2012-9-20
0 个投票
6 个评论
Walter Roberson
2012-9-20
The one line of code you show above would only convert the image and write it into the variable "gray" and would not display the image at all, and would not use a correct colormap in the display.
Please show us some code in which you can reproduce the problem.
Image Analyst
2012-9-20
Are you saying that you read the image using imread() into an array, and then you passed that image into rgb2gray() as Walter advised, and that you got an rgb image back out? I find that very surprising as I've never ever experienced that failure.
rgbImage = imread(filename);
grayImage = rgb2gray(rgbImage);
[rows columns numberOfColorChannels] = size(rgbImage)
[rows2 columns2 numberOfColorChannels2] = size(grayImage)
Run that code on your image and tell me what shows up in the command window. Please upload your original rgb image (which would be a BMP, TIFF, JPG, or PNG file, not a .fig file, and not a screenshot), and your code so I can verify before I submit a bug report.
Esther
2012-9-20
rows =
1936
columns =
2592
numberOfColorChannels =
3
rows2 =
1936
columns2 =
2592
numberOfColorChannels2 =
1
Walter Roberson
2012-9-20
Okay, and then what do you do with grayImage to display it?
Image Analyst
2012-9-20
编辑：Image Analyst
2012-9-20
So you DID get a gray scale image. Why did you say you did not?
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