Stil stuck on drawing SVGs from a folder

beginners
#1

trying to work the ofxsvg and directory list examples into one project that reads from a folder of of svgs and then outlines them on the screen.

It runs, but it just keeps drawing the same thing, the very first image in the folder.

q: why am I unable to iterate through the files in my folder?

I think I’m not getting something pretty fundamental about how reading and drawing works…

details

I have a series of svgs in a folder in bin/data.

variables

float step;
vector<ofPolyline> outlines;
vector<ofxSVG> images;
ofDirectory dir;
int currentImage;

my setup looks like this

void ofApp::setup(){
    
    ofSetVerticalSync(true);
    ofBackground(0);
    ofSetColor(255);
    ofSetFrameRate(60);

    


    dir.listDir("svgs");
    if ( dir.size()){
        images.assign(dir.size(), ofxSVG());
    }
    
    for(int i = 0; i < (int)dir.size(); i++){
        images[i].load(dir.getPath(i));
    }
    
    currentImage = 0;
    
    for (int i = 0; i < images[currentImage].getNumPath(); i++){
        
        ofPath p = images[currentImage].getPathAt(i);
        p.setPolyWindingMode(OF_POLY_WINDING_ODD);
        vector<ofPolyline> & lines = const_cast<vector<ofPolyline>&>(p.getOutline());
        
        for(int j=0;j<(int)lines.size();j++){
            outlines.push_back(lines[j].getResampledBySpacing(1));
        }
    }
    
}

then in update I say

if (step > 1) {
//from example
        currentImage++;
        currentImage %= dir.size();
        step -= 1;
    }

the draw function is exactly like the svg example, stripped down to the part I need…

void ofApp::draw(){
    
    ofPushMatrix();
    
    ofNoFill();
    
    for (int i = 0; i < (int)outlines.size(); i++){
        ofPolyline & line = outlines[i];
        
        int num = step * line.size();
        
        ofBeginShape();
        for (int j = 0; j < num; j++){
            ofVertex(line[j]);
        }
        ofEndShape();
    }

    ofPopMatrix();

any insight would be much appreciated :slight_smile:

#2

Hi there,

If, in svgExample, vector <ofPolyline> outlines; creates one group of polylines to draw one object, then you need something like vector <vector<ofPolyline>> outlines; so that you can have groups of groups of polylines.

After you load you SVG, you only loop through the first one: currentImage is always 0. You need to nest that loop inside another one and do the proper changes to you code.

#3

hey, thanks for the hints. So now I’m working towards setting up everything, so that draw just cycles through a vector where all my vectors of the paths are stored. I like that, I get that.

But I’ve tried a lot of different ways to do it and end up at the same problem every time: I get a runtime error that says bad access and outputs (lldb). For that, I find explanations about memory use (or solutions that point to something with xcode, but I doubt thats the problem…)

to get my head around it

   /*the group vector will have as many elemnts as there are pictures in the folder.
each picture is stored as a collection of paths. 
each path is simplified to a polyline (the outline of the path)*/
            //for every picture in the folder
                //for every path in the picture
                    //add all the polylines

maybe I’m not understanding how polylines are const and thats tripping me up?

void ofApp::setup(){

    ofSetVerticalSync(true);
    
    ofBackground(0);
    ofSetColor(255);
    
    dir.listDir("svgs");
    if ( dir.size()){
        images.assign(dir.size(), ofxSVG());
    }
    for(int d = 0; d < (int)dir.size(); d++){
        images[d].load(dir.getPath(d));
    }
    
    for (int c =0; c<images.size(); c++){
        
        for (int i = 0; i < images[c].getNumPath(); i++){
        
        ofPath p = images[c].getPathAt(i);
        // svg defaults to non zero winding which doesn't look so good as contours
        p.setPolyWindingMode(OF_POLY_WINDING_ODD);
        //lines is a refrence, remove the const from getOutline results (const bc of oF core stuff?)
        vector<ofPolyline>& lines = const_cast< vector<ofPolyline>& > (p.getOutline());
        
            for(int j=0;j<(int)lines.size();j++){
                outlines.push_back(lines[j].getResampledBySpacing(1));
            }

        }
        cout<<outlines.size() <<endl;
//and then the simplest imaginable solution...fails
        outlinesGroup[c]=outlines;
    }
}

o_O

#4

Hi,

Im still stuck on this problem. I have a vector of vectors of polylines called outlines group, and I’m trying to add a vector of polylines to it like so:

outlinesGroup[c]=outlines;

which trips up the program. Details in my post above. Any hints would be great.

#5

came across this project again and thought I’d update this in case anyone finds themselves here:

I just added

outlinesGroup.assign(images.size(),vector<ofPolyline>());

before the loop populating the outlinesGroup vector and it solved the runtime error…

cheers