how to convert image to rgb image to grayscale?

When using code mentioned in matlab examples, its working fine on 103X103 image but when applying same code on 512X512 image showing following error message. ??? Error using ==> rgb2gray>parse_inputs at 82 MAP must be a m x 3 array.

Error in ==> rgb2gray at 35 X = parse_inputs(varargin{:});

[Guillaume]

"i have just resized the 512x512 image to 103x103."

Yoy may have made a mistake in the way you resize the image. Post your code that does the resizing as well as the part with the rgb2gray call.

To post your code, just paste in a comment then click on the {}Code button to format it properly.

[monica sabharwal]

no... i have resized it through paint

Answer 1

[Star Strider]

It must already be a grayscale image, or an image with only one channel. The rgb3gray documentation says the input image has to be a truecolour 3D numeric array.

[monica sabharwal]

both the images are same 512x512 and 103x103. i have just resized the 512x512 image to 103x103.

[Star Strider]

The documentation states under Input Arguments that the image must be ‘Truecolor image, specified as 3-D numeric array.’

Your images are 2D, likely already grayscale.

Post your images using the brown-framed green picture icon, or the ‘paperclip’ icon. Complete both steps for the one you choose.

[Image Analyst]

I agree with Star - your image is already grayscale. What does this say

[rows, columns, numberOfColorChannels] = size(yourImage)

Don't put a semicolon after that line. Tell us what you see in the command window.

[monica sabharwal]

for (512X512)

[rows, columns, numberOfColorChannels] = size('1.jpg') giving result 1,9,1

 for(103X103)

[rows, columns, numberOfColorChannels] = size('1.jpg') giving result 1,5,1)

[Walter Roberson]

IM512 = imread('1.jpg');   %read the 512 x 512 image
[rows, columns, numberOfColorChannels] = size(IM512)

IM103 = imread('1.jpg');   %read the 103 x 103 image
[rows, columns, numberOfColorChannels] = size(IM103)

You cannot use rgb2gray on an image name, you have to use it on the content of an image.