Color SURF detector

Question

SURF by default works on Gray image. I am thinking to do SURF on HSV image. My method is to separate the channels into H, S and V. And I use S and V for keypoint detection. I t

Answer 1

2. Can we apply SURF to color, HSV space?

I didn't test it, but as far as I know, SIFT and SURF use quite (in principle) similar detection techniques:

SIFT detector uses the Difference-of-Gaussian (DoG) technique to efficiently approximate the Laplacian-of-Gaussian (LoG), which both are Blob Detection techniques.

SURF detector uses box-filters/box-blurs of arbitrary size to compute (or approximate?) The determinant of the Hessian which is a Blob Detection technique.

Both methods use some strategy to compute those blobs in multiple scales (SIFT: DoG-Pyramid; SURF: integral images to scale the filter sizes). At the end, both methods detect blobs in the given 2D array.

So if SIFT can detect good features in your (H)SV channels, SURF should be able to do the same because in principle they both detect blobs. What you will do is detecting blobs in the hue/saturation/value channel:

• hue-blobs: regions of similar color-tone which are surrounded by different (all higher or all lower) color-tones;

• saturation-blobs: regions of... yea of what? no idea how to interpret that;

• value-blobs: should give very similar results to the grayimage converted RGB image's blobs.

One thing to add: I'm just handling the detector! No idea how SIFT/SURF description is influenced by color data.

Answer 2

I didn't test it, but what you could do is using the interest point HSV values as additional matching criteria. What I used in the original implementation and what speeded up matching image pairs was the sign of the determinant of the Hessian matrix. The sign tells us whether it is a light blob on a dark background or a dark blob on a light background. Obviously, one would not attempt to match a dark blob with a bright blob.

In a similar way, you could use HSV values and use the distance. Why matching blue blobs with yellow blobs. Makes no sense, except white balance or lighting is completely messed up. Maybe my paper about matching line segments can help here. I used HSV there.

As for extracting SURF interest points on the different channels H, S, and V, I agree with the answer of Micka.

What you could try is to make a descriptor using the Hue channel.