How to set the alpha value of a copy of a PImage?

danielle_nl

Hi all,

I'm struggling to find a way to make a part of an image created with copy() transparent. The images are preloaded into an array in setup(). I don't display the original images. I loop through the loaded images in draw() and use copy() to create a resized slice of the images. Is there a way to add transparency to these slices? I could also make the original transparent because it isn't displayed anyway. I tried using tint() in setup before loading but that doesn't work.

Any help is highly appreciated, best, Danielle.

KevinWorkman

The PImage class has a set() function that takes a color. That color can contain an alpha value. If that's not working, please post an MCVE showing exactly what you're doing.

Reference for the set() function: https://www.processing.org/reference/PImage_set_.html

GoToLoop

• Find out which color should be made transparent on those PImage objects.
• Much probably it's black (#000000).
• Iterate over each PImage's pixels[], for example changing each #000000 found to 0.
• Don't forget updatePixels() after each iteration is over.

danielle_nl

Hi guys, thanks for your answers. The thing is that I want to set alpha for a picture... Here is some very simplified code to illustrate:

PImage[] images = new PImage[278];
        int stripSize = 10;
        void setup(){
          for (int i = 0; i < images.length; i ++ ) {
              images[i] = loadImage("pics/"+(i+1) + ".png");
           }
        }
        void draw(){
          for (int i = 0; i < images.length; i ++ ) {
            float yPos = 10;
            copy(images[i],(images[i].width/2-(stripSize/2)),0,stripSize,images[i].height,i*stripSize,height-int(yPos)-(images[i].height/2),stripSize,images[i].height/2);
          }
        }

So I want to set the copied part, the entire image strip, to a transparency of 10% for example. As I explained above I could even manipulate the originals as they are not shown. But I can't get that to work either. Thanks in advance for your help, best, danielle.

PhiLho

Use loadPixels(), iterate on the pixels[] array, set the high byte of each entry to the alpha value of your choice.

danielle_nl

Thanks FhiLho, what is the high byte?

PhiLho

See http://forum.processing.org/two/discussion/8086/what-is-a-color-in-processing#latest in the Common Questions categtory...