clearing the screen without calling to background() for PDF export

Core Library Questions

artcodeem..

clearing the screen without calling to background() for PDF export

in Core Library Questions • 2 months ago

Hello all:

I always use background(value) to clear the screen before generating a new execution of my algorithm, animation, etc.

The problem is that I don't know how to clear the screen without using background(value) and I couldn't find any way to do it in this forum or google.

The reason why I want to avoid using background(value) is that I want to export several PDF files with transparent background.

When I don't call to background(value) this happens: the PDF gets exported without background (as I want).

Any advice?

Thanks in advance for your reply.

Replies(13)

tfguy44

Re: clearing the screen without calling to background() for PDF export

2 months ago

You can't really do transparency in the main window, because it's background is always solid.

Try rendering things to PGraphics objects instead. They can do real transparency.

size(400,400);
background(0,128,0); // Main window is solid green.
PGraphics pg = createGraphics(width,height,P2D);
pg.beginDraw();
pg.background(0,0,0,0); // Make bg transparent
pg.noStroke();
pg.fill(255,0,0);
pg.rect(20,20,30,40); // Draw a solid red rectangle.
pg.endDraw();
image( pg.get(), 0, 0 ); // Draw image with transparency over solid green background.

PhiLho

Re: clearing the screen without calling to background() for PDF export

2 months ago

" When I don't call to background(value) this happens: the PDF gets exported without background (as I want)."

If that's what you want, what is your problem then?

Perhaps you want to make PDF files with several pages, one per run of the algorithm?

artcodeem..

Re: clearing the screen without calling to background() for PDF export

2 months ago

Thank you very much tfguy44!

This is exactly what I would do if I used pixel images as my final output but for these projects I want vectors so the solution you give me it's cool, works, I knew it but doesn't apply to this case. Sorry! I am sure other people will find it useful though!

I need to use PDF with vectors (and not images) because I want to:

1) Preserve vector editability in Illustrator

2) I need to magnify as much as I want

If you don't set any background in your sketch, for example:

void setup() {
size(400, 400);
//your code here without background(0)...
// ....
}

and then you export the PDF using beginRecord(PDF, "myFile.pdf"), it won't have any background as I need.

But then the problem is that I cannot clear the screen and generate another vector.

That's the main reason of this post.

Any ideas guys?

Thanks a lot.

artcodeem..

Re: clearing the screen without calling to background() for PDF export

2 months ago

Many thanks for your reply PhiLho

If that's what you want, what is your problem then?

My problem is that, without closing the sketch and relaunching it, I want to generate multiple results. So I want to clear the screen and generate another execution (another vector) using the same algorithm with slightly different values.

Thanks a lot!

PhiLho

Re: clearing the screen without calling to background() for PDF export

2 months ago

I still don't see where the problem is. If the new execution is on the same page, just draw it over the previous one. If it needs to be on another page, just use nextPage(). If it needs to be on another file, just close the previous one and open a new one.

artcodeem..

Re: clearing the screen without calling to background() for PDF export

2 months ago

If I use nextPage() then I will create a new page in my PDF but I don't want this.

The basic process I want to follow is:

1) I run the sketch

2) A vector is generated

3) I save it in a PDF file

4) I want the vector generated in the step 2 to disappear from the screen (so the new one I am about to generate doesn't get mixed with the generated in step 2)

5) Back to step 2

My question is about how to make the vector disappear from the screen in my step 4

Thanks a lot!

artcodeem..

Re: clearing the screen without calling to background() for PDF export

2 months ago

While we find a solution, I have created this script for illustrator (name it with the extension .jsx) and I thought about sharing it with you guys:

var idoc = app.activeDocument;
var bottomLayer = idoc.layers[idoc.layers.length-1];
idoc.activeLayer = bottomLayer;
var bottomPath = bottomLayer.pathItems[bottomLayer.pathItems.length-1];
bottomPath.selected = true;

That will select the background of my PDF, so I can automate a batch process for my PDFs that removes all the backgrounds for me.

Hope you find it is useful!

For sure, the coolest would be to generate my PDF with that background!

dimkir

Re: clearing the screen without calling to background() for PDF export

2 months ago

Dear artcodeemotions,

i am trying to undrestand what you are trying to accomplish and here's my understanding, I wonder if you can correct me where my understanding is wrong:

a) generate vector and display it on screen

b) save vector to PDF (? when mouse is clicked? when generation is complete? )

c) you want to clean screen (meaning your LCD monitor right? not the pdf?)

d) and now you want to generate new vector on screen? ( but what happens with PDF? does it stay open? or you close it? or nextpage? or you close and open new one for the next vector?

artcodeem..

Re: clearing the screen without calling to background() for PDF export

2 months ago

Many thanks for your help dimkir

a) correct, using beziers, etc

b) correct. When the generation is complete

c) yes, my screen. The pdf now is created, completed, and close. For the next vector I will generate a new pdf file

d) yes, a new vector on the screen, the new vector will be recorded to a new pdf file.

So if I create 10 vectorial shapes, each shape gets recorded in one PDF file ending with 10 PDF files.

I want to avoid each vector to overlap by clearing the screen each time I generate a new vector.

dimkir

Re: clearing the screen without calling to background() for PDF export

2 months ago

and do you need shapes as Vectors inside PDF or as raster image? (because i have a feeling that now when you're saving your vectorial shapes to PDF with image() they all turn into pixels)?

artcodeem..

Re: clearing the screen without calling to background() for PDF export

2 months ago

I need them as vectors to preserve maximum editability in Illustrator, not raster image.

Currently when I save the PDF, the vectors are preserved properly, not turned into raster images. The only thing that I don't want in that PDF is the background.

Thanks a lot!

kooogy

Re: clearing the screen without calling to background() for PDF export

2 months ago

if you're using beginRecord / endRecord to write multiple files (part c in your list), can you clear the screen before the beginRecord()? that way it should clear the visible screen but won't be written to the pdf

artcodeem..

Re: clearing the screen without calling to background() for PDF export

2 months ago

kooogy you hit the nail!

that is exactly what I wanted. That was a very smart answer that I didn't think of.

thank you very much indeed and in general to all of you that have tried to help me :) :)

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