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My new GitHub account
Hi there, I just created one account on GitHub, and added a GPL license on all the samples published so far on this site. Find everything in this repository : https://github.com/gaeljaffrain/Image_Processing_Tutorials As a comment, I find the new GitHub client very handy, and way more user friendly that the existing clients for Git. With this client,…
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Contrast enhancement – part 2/2
All right, now that we added some missing bricks, like Y’CbCr to RGB , we can finish our contrast enhancement started in the post Contrast enhancement – part 1/2. The goal is to tweak poor contrast images, like this one: And to make these pictures automatically and reasonably contrasted: So let’s summarize, the idea is…
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Embedding a Processing.js sketch in a WordPress page
Processing.js is very handy, and it is very cool to run your sketches in your browser. I was looking around for one easy way to embed a sketch into a WordPress page or post, and found a good option. I used the Processing JS plugin, written by Keyvan Minoukadeh. You can get it from this…
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Color saturation enhancement and Y’CbCr to RGB conversion
Before finishing the contrast enhancement started in previous post, we need to add a Y’CbCr to RGB function. It will allow us to close the loop : RGB=>Y’CbCr=>contrast enhancement on Y’=>RGB. One easy modification we can do while in Y’CbCr domain is modifying color saturation by multiplying Cb and Cr by a common gain. Finally,…
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Contrast enhancement – part 1/2
In the previous image processing posts, we built a luma histogram from a RGB picture. In the next posts, we will work on contrast enhancement. We will use the luma channel, and define 2 luma stretch points, one on the dark side, one on the bright side. So all the pixels having a luma value…
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Macro photography with a smartphone ? DIY !
Creativity is often allowing us to solve some nice problems. Like, let say, taking macro photo without a macro lens. Plenty of tricks exist and can best be done with interchangeable lens cameras. These tricks include : using the lens upside down, adding a lens element, using extension tubes … Many websites can explain these…
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Luma histogram
In the previous post we created 3 channels from the RGB original picture : Y’, Cb, and Cr. We will now look that the luma histogram, so using the Y’ channel computed in previous post. What is an histogram ? It is a graphical representation of the pixel value distribution in a picture. It could…
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Y’CbCr (“YUV”) conversion – part 2
Now the fun part : the implementation using Processing.js We will load the original picture as in the previous example: img = loadImage(“Yosemite.jpg”); Then we will go through all the pixels by 2 loops: for (int y = 0; y < img.height; y++) { //we loop through every line for (int x = 0; x…
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Y’CbCr (“YUV”) conversion – part 1
Ok this week let’s try something a little bit more useful than random manipulation of one picture. Starting from the same beautiful Yosemite picture, we will convert it from RGB color space to Y’CbCr color space. Many websites can help you to get more background on Y’CbCr color spaces, and commonly called “YUV”. I am…