Processing 1.0 - Processing Discourse - How to save a png with transparency?

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Index › Programming Questions & Help › Syntax Questions › How to save a png with transparency

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How to save a png with transparency? (Read 657 times)

DoctorEternal

How to save a png with transparency?
Oct 4^th, 2007, 11:14pm

I want to save a generated image as a PNG, with the alpha channel so when I load it back into a PImage it'll be transparent.

Using save("file.png") does not do this (it just fills in with the bg color.

How can this be done?

PImage line;

void setup() {
size(400,400);
frameRate(15);
}

void draw() {
noStroke();
fill(150, 150, random(255));
rect(random(width), random(height), random(120), random(120));
filter(BLUR, 2);
}

void mousePressed() {
save("line.png");
}

When I click the mouse, I'd like the areas not drawn to be the ALPHA.

Thanks!
Dr.E

extrapixel

Re: How to save a png with transparency?
Reply #1 - Oct 5^th, 2007, 12:02am

hi,

i think you'll need an extra PGraphics object for this.
http://processing.org/reference/createGraphics_.html
http://processing.org/reference/image_.html

This is how I did it:
Quote:

PGraphics alphaG;

void setup() {
size(400,400);
// create an extra pgraphics object for rendering on a transparent background
alphaG = createGraphics(width,height, JAVA2D);

// background will be transparent in the png-file
background(0);
}

void draw() {

// draw into the pgraphics object
alphaG.beginDraw();
alphaG.fill(255,100);
alphaG.rect(random(width), random(height), 30,30);
alphaG.endDraw();

// draw the second renderer into the window, so we can see something
image(alphaG, 0,0);
}

void keyPressed() {
alphaG.save("alphatest.png");
println("alphatest.png saved.");
}

http://www.extrapixel.ch

DoctorEternal YaBB Newbies Offline Posts: 11 USA	Re: How to save a png with transparency? Reply #2 - Oct 5^th, 2007, 12:22am Perfect! Thanks!

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