How I Did My Image Processing
Simple steps that will allow you to do it yourself - part 2
The first step in real image processing is to try and sharpen or enhance features without actually corrupting the data that the image contains. Small changes in image brightness and contrast can actually have large effects, but typically can be done pretty freely.
Because of how the human visual system works, we tend to find objects within a narrow range of brightnesses best. But the details can be brought out with simple methods.
| The first
step is to produce a negative of the image to be enhanced. This is
done by duplicating the image and then inverting it.
Here is the negative of the original picture. |
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| Now we use an
"overlay" function with 50% transparency to stitch one image
over the other one. This will add together the positive and negative
portions of the image and result in a neutral gray in most areas.
But overlaying the images exactly on top of each other will completely cancel them both. So what we have to do is provide a slight offset of one pixel right and one pixel down- this will enhance only the sharp edges and create an image that is just differences. This is exactly what we want. I have enhanced the contrast by 50% to sharpen and amplify the edge data. This is very similar to an "emboss" function. See the flat thing below the spherule? It looks like a sand dollar, complete with serrated edges. |
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| Now we add the
new amplified difference data to the original image to bring out the
contrasts. You will get a picture that has its "sharpness"
greatly increased, but with very little cost in terms of image data.
See how every grain of sand now stands out? And there are clear features available on the fossils now that you can pick out by eye, where before, they were "mushier" and harder to discern. Of course, this process also amplifies the noise in the image, and JPEG artifacts become a problem. But we can counter this by doing a slight blurring of the image. Don't worry, this actually helps to eliminate noise. And yes, that IS a sand dollar beneath the "Jupiter" fossil. |
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