Save/Load an ArrayList file of PGraphics To/From a text file

Programming Questions

XYZZY

Save/Load an ArrayList file of PGraphics To/From a text file

in Programming Questions • 2 months ago

I'm hoping for a little direction on something. In a sketch I create an ArrayList of PGraphics, starting with just one image. The image can be drawn on with the mouse. Using the right arrow key you can create a new PGraphics and draw on that as well. The right and left keys serve to flip between the PGraphics. I would like to create a function to save all of the PGraphics to a file and another function to load them again.

I've been looking around for info on this and have some ideas, but nothing has been obvious enough for me to understand. Any help would be appreciated. Here is the simplified code of what I am working on:

int currentPage = 1;
ArrayList<PGraphics> pageCollection = new ArrayList<PGraphics>();
void setup(){
size(400,400);
background(255);
pageCollection.add(createGraphics(300,300));
pageCollection.get(0).beginDraw();
pageCollection.get(0).background(200);
pageCollection.get(0).endDraw();
}
void draw(){
frame.setTitle("Page " + currentPage + " of " + pageCollection.size());
background(255);
image(pageCollection.get(currentPage-1),50,50);
g.removeCache(pageCollection.get(currentPage-1)); //memory leak prevention
}
void mouseDragged() {
makeMark();
}
void makeMark() {
pageCollection.get(currentPage-1).beginDraw();
pageCollection.get(currentPage-1).smooth();
pageCollection.get(currentPage-1).stroke(0);
pageCollection.get(currentPage-1).line(pmouseX-50,pmouseY-50,mouseX-50,mouseY-50);
pageCollection.get(currentPage-1).endDraw();
}
void keyPressed() {
switch (keyCode) {
case LEFT: //scroll left through pages
println("###### Go Back One Page ######");
if (currentPage == 1){
currentPage = 1;
}else {
currentPage -=1;
}
break;
case RIGHT: //scroll right through pages
println("###### Go Forward or Add One Page ######");
if (currentPage < 300) {
if (currentPage == pageCollection.size()){
newPage();
}else {
currentPage +=1;
}
}
break;
case UP: // save the ArrayList to file
println("###### Save All Pages ######");
// call save function
savePages();
break;
case DOWN: // clear the current ArrayList and load a file into ArrayList
println("###### Load Pages ######");
loadPages();
break;
default:
println("###### keyCode error ######");
}
}
void newPage() {
pageCollection.add(createGraphics(300,300));
pageCollection.get(currentPage).beginDraw();
pageCollection.get(currentPage).background(200);
pageCollection.get(currentPage).smooth();
pageCollection.get(currentPage).stroke(0);
pageCollection.get(currentPage).endDraw();
currentPage +=1;
}
void savePages() {
// code for saving pages to a text file
}
void loadPages() {
// code for clearing the current ArrayList and loading the ArrayList from a text file
}

Replies(4)

GoToLoop

Re: Save/Load an ArrayList file of PGraphics To/From a text file

2 months ago

Since it's pretty regular Java stuff, I did some searchings for it and found lotsa it.
http://www.rgagnon.com/javadetails/java-0075.html
http://stackoverflow.com/questions/10654236/java-save-object-data-to-a-file

XYZZY

Re: Save/Load an ArrayList file of PGraphics To/From a text file

2 months ago

Excellent. That is a good start. Being new to this, I'm not always sure where to start. Thanks.

dimkir

Re: Save/Load an ArrayList file of PGraphics To/From a text file

2 months ago

Well serialization is an important part of Java, but imho a bit too complicated for a beginner. And it probably will take about a month to understand all the "slippery" spots of serialization.

At the same time it seems (i may be wrong) that all you need to do is just to save the "pixels" of the pgraphics to a file. In the title of the thread you mentioned saving PGraphics object, but from the project description it seems that all you have to do is just save "image information" (the pixels) of the graphics to image file. And later you can create graphics from an image as well. To do that you need two methods:

/**
* Saves graphics to image file. Speficy filename with extensions:
* .png .tiff .tga .jpg
* just like with image.save() method.
*/
void saveGraphicsToFile(PGraphics gr, String filename){
gr.save(filename);
}
/**
* Creates new graphics from the image file.
*/
PGraphics loadGraphicsFromFile(String filename){
PImage img = loadImage(filename);
PGraphics gr = createGraphics(img.width, img.height, JAVA2D);
gr.beginDraw();
gr.image(img,0,0);
gr.endDraw();
return gr;
}

hope this helps

XYZZY

Re: Save/Load an ArrayList file of PGraphics To/From a text file

2 months ago

Thanks, dimkir. I was hoping to save all of the images in the ArrayList into one file, .dat or .txt or .ser or whatever. After looking into that some, I think it is a little more than I want to bite off right now, but I still want to do it at some point.

I did work out a for-loop to save each PGraphics as an image into a folder, though I need to work out a better way to include the ArrayList's index number in the file name, i.e. - have leading zeros so that index "5" outputs as 0005. I think the saveFrame() function might work for this, but I haven't figured that out yet for PGraphics in an ArrayList.

That all deals with the saving part, but I still need to work on the loading. I'm hoping to work out selecting the first png in a sequence and then all pngs in that sequence are loaded. This will require some filename filtering and I'll need to do some reading on that. I have some code snippets for multi-file selection and I might just go with that.

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