MATLAB: Image Processing: Detect Quartz Veins in Photos

image processing

Hi,

I was hoping to get some help. I'm trying to automate a procedure to detect quartz veins in core photos from a mining database. I've converted the images to binary using a variety of gray theshold values. The problem is that it detects too much of the wooden box, tags etc.

If I manually crop out just the rock, the results are much better. This is unrealistic through because I need a way to batch process.

Here is the original photo and a binary version. As you can see, too much of the box is selected and a bunch of other stuff. I need to select only the white quartz veins that cut through the gray rock.

I'm quite new to image processing so I apologize if this is a fairly simple problem.

Thanks for your help!

Best Answer

It's not a simple problem. On the face of it, it might look simple but I can foresee all kinds of possible problems. What I would start off with is doing color segmentation - basically find the brown pixels. See my File Exchange for examples. http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862

But there might be cases where the "white" marble is very close in color to the light brown wood. Have you looked at the 3D color inspector to see the full 3D color gamut? As you can see below, there is quite a bit of overlap/blending between the colors. It's not like you have 3 very well separated colors.

Related Solutions

MATLAB: Color segmentation of skin markers: HSV or Lab? How to choose thresholds

Matt, welcome to the interesting field of image analysis - I think you'll find it fun and interesting to work with pictures. HSV is kind of like LAB color space except that you're using cylindrical coordinates instead of cartesian coordinates. So like in any regular 3D space, you can specify x,y,z or if you'd prefer, you can use radius, angle, and height. With either method you can specify a point/coordinate in the 3D space. It's the same with LAB and HSV (well almost but that's good enough for now).

So, cartesian space, LAB space, is good for thresholding or carving out rectangular boxes. Cylindrical space, HSV space, is good if you need to carve out a pie-shaped sector from the color space. It would be good if you could download ImageJ and use the Color inspector 3D ( http://rsb.info.nih.gov/ij/plugins/color-inspector.html) and install it so you can see your color image's gamut in the different color spaces so you can see which space is best to threshold in. Maybe later tonight I can capture a screenshot of your image and upload it.

MATLAB: Is it possible to have a custom color bar

Try this:

grayImage = imread('cameraman.tif');
% Rescale image to values -25 to 5600.
grayImage = rescale(double(grayImage), -25, 5600);
imshow(grayImage, []);
light_brown = [0.95 0.9 0.8];  
brown_color = [0.8 0.2 0.1];
numColors = 256; % Whatever
redMap = linspace(light_brown(1), brown_color(1), numColors);
greenMap = linspace(light_brown(2), brown_color(2), numColors);
blueMap = linspace(light_brown(3), brown_color(3), numColors);
myColorMap = [redMap(:), greenMap(:), blueMap(:)];
colormap(myColorMap);
colorbar;
caxis([-25, 5600]);

Best Answer

Related Solutions

MATLAB: Color segmentation of skin markers: HSV or Lab? How to choose thresholds

MATLAB: Is it possible to have a custom color bar

Related Question