how to find the color gradients of natural scene image

I have wang database . I need to extract Color gradients as the image features of natural scene images. can you plz help how to extract color gradient features form natural scene images..

thankk you

and I am using current trial version of matlab.

[Image Analyst]

What is your definition of the "Color" gradient? As you know, color is a 3-dimensional property, like RGB or HSV. Do you want imgradient() of the gray scale image or the V image, or of the Hue image? Or the saturation image? Please give a mathematical definition.

[hp]

I am working on Image retrieval. I need to retrieve similar images from collection of images. I have 20 classes, beach, buildings, bus, car, butterfly and so on. I wanted color gradients as a features to efficiently retrieve the query relevant images. Can you plz help me whether grayscale image suits or color(RGB or HSV) for this task and how to implement in matlab?

Kindly do help ...

Thank you..

Answer 1

[Image Analyst]

You didn't answer my question so all I can suggest is to look at imgradient() or imgradientxy().

[hp]

Thank you. I will verify.