Does PDF Not Play With Matrices?

Core Library Questions

artsnova

Does PDF Not Play With Matrices?

in Core Library Questions • 1 year ago

Hi,
I had a rather complex Processing program and thought it would be nice to output to a PDF in addition to the screen. Unfortunately it blows up with a "missing a PopMatrix() error"

So I created the following very simple program that preserves the core characteristics of my real program in order to see what would happen:

import processing.pdf.*;
float offsetX,offsetY;
boolean wipe=true;
void setup(){
size(1200,800);
offsetX=width/2;
offsetY=height/2;
beginRecord(PDF, "testingpdf.pdf");
noLoop();
}
void draw(){
drawit();
noLoop();
}
void drawit() {
float x,y;
rectMode(CENTER);
translate(offsetX,offsetY);
for(int n=0; n < 50; n++) {
fill(random(0,255),random(0,255),random(0,255));
x = random(0,width);
y = random(0,height);
pushMatrix();
translate(x,y);
rotate(radians(random(0,TWO_PI)));
rect(0,0,random(20,100),random(20,100));
popMatrix();
}
}
void mousePressed() {
offsetX=mouseX;
offsetY=mouseY;
if(wipe) background(255);
loop();
}
void keyPressed() {
if(key=='x' || key=='X') {
// output file
endRecord();
println("Quit and Saved ");
exit();
}
}

The program works fine until I add the begin and end record statements for the PDF. When I press 'x' to save, I get this error:

Exception in thread "AWT-EventQueue-0" java.lang.RuntimeException: missing a popMatrix() to go with that pushMatrix()

Taking another charge at it, I modified the program as follows:

import processing.pdf.*;
float offsetX,offsetY;
boolean wipe=true;
void setup(){
size(1200,800);
offsetX=width/2;
offsetY=height/2;
beginRecord(PDF, "testingpdf.pdf");
}
void draw(){ }
void drawit() {
float x,y;
rectMode(CENTER);
translate(offsetX,offsetY);
for(int n=0; n < 50; n++) {
fill(random(0,255),random(0,255),random(0,255));
x = random(0,width);
y = random(0,height);
pushMatrix();
translate(x,y);
rotate(radians(random(0,TWO_PI)));
rect(0,0,random(20,100),random(20,100));
popMatrix();
}
}
void mousePressed() {
offsetX=mouseX;
offsetY=mouseY;
if(wipe) background(255);
drawit();
}
void keyPressed() {
if(key=='x' || key=='X') {
// output file
endRecord();
println("Quit and Saved ");
exit();
}
}

The popMatrix error message goes away but is replaced with the following message:
isRecording(), or this particular variation of it, is not available with this renderer.

Note that these errors do not occur if I write to the PDF file using size(w, h, PDF, "filename");
instead of the begin and end record statements.

Unfortunately this method means no screen output and I really do need to be able to see what I'm doing before deciding whether or not to create the PDF.

Any suggestions would be appreciated. Thanks

Best Regards, Jim

Replies(3)

PhiLho

Re: Does PDF Not Play With Matrices?

1 year ago

Funny, even if I remove your push/pop matrix calls, I get the same error, so it might be a Processing bug, as the code looks OK.
Note: even if it worked, I don't think it will do as you expect: save to PDF doesn't work like save() or saveFrame(). It has to record the drawing actions live. So it would save virtually all the frames you saw before pressing x.

Your second code works, apparently the error message is actually just a warning.
Note that you have only one frame as result, but actually all drawings are recorded, that's just the last background() call that hides the previous attempts.
In other words, if you do lot of clicks before choosing the image, the resulting file will be bigger (and slower to open) than if you did few clicks.

artsnova

Re: Does PDF Not Play With Matrices?

1 year ago

Hi PhiLho,

First I was able to eliminate the error. I did this by moving the method that was being called by draw() into draw() itself (not a practical solution for the actual program). Second I replaced the loop()/noLoop() combo with a boolean variable to indicate a draw/no draw state. The program then worked like a charm. While I did still get the "isRecording()..." error the data was correctly written to the PDF.

With respect to the number of frames drawn, first off Photoshop is nightmarishly slow at reading the PDF vectors. So you're right - you really want to watch that frame count since Photoshop (and Acrobat) will read through all the vectors one frame at a time.

Re frames that was the point of the loop control. I do only want to output one frame In my original program, each click produces a list of variable values. Once I have a frame I like, I escape from the sketch and use those values as the new initial conditions to produce a single frame PDF. Note sure if my attempts to explain what I'm doing makes sense.

An alternative approach, which I have not tried, is to have a separate routine that executes the begin/end record with a call (if possible without getting the popMatrix error) to the last set of draw instructions executed.

As always, thanks for your feedback.

Best Regards, Jim

PhiLho

Re: Does PDF Not Play With Matrices?

1 year ago

I thought of yet another alternative: just write one frame in the PDF, each time, overwriting the previous one. When you see something that pleases you, move it elsewhere, perhaps numbering it.

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