Video pixel information to make a second transparent layer

Core Library Questions

tsiwt19

Video pixel information to make a second transparent layer

in Core Library Questions • 3 years ago

Hello all , I am new to processing so could you help me figure this out, how to go about making it, even if is possible.

I want to import a video and get specific pixel data such as color, brightness, and then use the location of the color or data to make a sketch that draws very small lines or ellipses etc that are then overlaid on top of the specific pixels of the video.

so the video of example -> the sky would have all the blue of the sky overlaied with very small red ellipses but nevertheless you can see the white clouds of the video moving through because I haven't affected the white in the video

please help.

thanks

Replies(3)

owaunandr..

Re: Video pixel information to make a second transparent layer

3 years ago

If you can post the code, we may post a snippet to help since processing is so powerful there are numerous ways to do this.

I find creating a PGraphics object is the best solution. This method allows you to draw ellipses, rects, etc as if you were referencing a sketch. Then you just simply super impose it over the video.

The other solution is to use createGraphics with a transparency level of between 105 and 205. This has its limitations as you can only manipulate pixels and not create shapes like you indicated in your post. The benefit of this method is that you can refer it directly without having to remember to <pgraphic>.beginDraw() <pgraphic>.loadPixels() and <pgraphic>.updatePixels() <pgraphic>.endDraw() every so often.

However, each has its pros and cons.

ickydog

Re: Video pixel information to make a second transparent layer

3 years ago

From the Brightness Tracking example, first, just as a generic "go through the video frame and look at each pixel":

for (int y = 0; y < video.height; y++) {
for (int x = 0; x < video.width; x++) {
// Get the color stored in the pixel
int pixelValue = video.pixels[index];
// Determine the brightness of the pixel
float pixelBrightness = brightness(pixelValue);
// If that value is brighter than any previous, then store the
// brightness of that pixel, as well as its (x,y) location
if (pixelBrightness > brightestValue) {
brightestValue = pixelBrightness;
brightestY = y;
brightestX = x;
}
index++;
}
}

Next, something like this might get you started with alpha channel manipulation. I use it to strip the Alpha channel bc it tends to come in from the webcam completely opaque.

If the bitshifting parts makes your head spin, check out the other tutorials:

for (int i = 0; i < w*h; i++) {
color currColor = _tempImg.pixels[i];
color prevColor = previousFrame[i];
int currR = (currColor >> 16) & 0xFF;
int currG = (currColor >> 8) & 0xFF;
int currB = currColor & 0xFF;
int prevR = (prevColor >> 16) & 0xFF;
int prevG = (prevColor >> 8) & 0xFF;
int prevB = prevColor & 0xFF;
// Compute the difference of the red, green, and blue values
int diffR = abs(currR - prevR);
int diffG = abs(currG - prevG);
int diffB = abs(currB - prevB);
_tempImg.pixels[i] = 0xff000000 | (diffR << 16) | (diffG << 8) | diffB;
previousFrame[i] = currColor;
}

Note that previousFrame is an int[] array declared at the top of the sketch equal to [w*h].

C
--
/biting at the ankles of giants/

tsiwt19

Re: Re: Video pixel information to make a second transparent layer

3 years ago

thanks for the answer this is got me started .

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