Cleaning pixels from a map

We have this map, we need to use PHP to take all the shades of blue out, as well as the percentages. The problem is, is that some of the percentages开发者_开发问答 are in the same color as the borders, and other times, the percentages go into the border. We need to use this image.

There are not (AFAIK) really easy ways.

The easiest way doesn't give you good results: separate channels and delete small components.

The result is this:

As you can see there are a few numbers and percent signs remaining because they are connected to the delimiting lines and deleting small components doesn't work for them.

If you need a better job, you should correlate the image with a template of each number, and once identified, delete it.

Here you can see the result of the correlation with the number "2":

One wrong "2" is identified, (see top left), so a more sophisticated approach may be needed for a general procedure.

Anyway, I think these kind of manipulation is well beyond what you can expect from K-12.

HTH!

Edit

As per your request, some detail about the first method.

You first separate the three channels, and get three images:

You keep the third (the blue channel)

Then you need to delete the smaller components. There are a lot of methods to do that, probably the easiest is derived from the connectivity detection for example in the flood-fill algorithm, but you just measure the components without filling them.
The basic (not optimized) idea is to travel every pixel in the image and count how many pixels are "connected" with it. If there are less than a specified number (threshold), you just delete the whole set. Most image manipulation libraries have all these functions already implemented.

For this specific image, if you open the image in image editing software, convert the mode from index to true color (RGB), and then color dodge the entire image with yellow (RGB: 255,255,0), you wind up with a black and white image consisting of the outlines and numbers. (this is also what the blue channel looks like BTW)

So either throw away the red and green channels, or implement a color dodge algorithm.

Another alternative is to sample each pixel, and the set that pixel's R & G components to the B value

edit: actually, I forgot about the white numbers. to get those, flood fille the outer white with the rgb(0,0,255), invert the entire image, and color dodge with (255,255,0), the red or green channel is now the missing numbers. Overlay these on top of the processed image from previous steps above.

Getting rid of the shaded colors should be easy.

Getting rid of the numbers is more tricky. I would:

• Make a lookup table of the pixel data associated with each number and the % sign.
• When clearing an area, look for the numbers (black or white) and only clear out exact patterns from the lookup table.
• Recreate the border between areas by adding a black color between different shades.

It's impossible to do this with guaranteed accuracy simply because the digits hide original information. However, I think the above steps would give you close to 100% accuracy without a lot of effort.