Setting (0,0) to bottom-left without switching X- and Y-axis in Processing(.org) - processing

Question

I'd like to change the coordinate system in a 2d processing sketch, putting (0,0) in the bottom-left rather than the top-left. The following code will move (0,0) to the bottom-left:
transform(0, height);
rotate(radians(-90));
However, it also makes the X-axis the vertical axis. Is there a simple way to move (0,0) to the bottom-left and keep the X-axis horizontal?
One option I've considered is using P3D with a combination of rotate and rotateY, but would prefer a solution for the 2d case.
Thanks for any help!

Answer 1

You could simply translate without rotating:
transform(0, height);
And handle your coordinates as flipped:
boolean useVFlip = true;
void setup(){
size(400,400);
}
void draw(){
background(255);
if(useVFlip) translate(0,height);
drawAxes(100);
translate(width * .5, useVFlip ? (height-mouseY)*-1 : mouseY);
triangle(0,0,100,0,100,100);
}
void keyPressed(){ useVFlip = !useVFlip; }
void drawAxes(int size){
pushStyle();
strokeWeight(10);
stroke(192,0,0);
line(0,0,size,0);
stroke(0,192,0);
line(0,0,0,size);
popStyle();
}
If it makes it easier to get flipped coordinates, you could flip the whole coordinate system using the scale() method:
boolean useVFlip = true;
void setup(){
size(400,400);
}
void draw(){
background(255);
if(useVFlip){
scale(1,-1);
translate(0,-height);
}
drawAxes(100);
translate(width * .5, useVFlip ? height-mouseY : mouseY);
triangle(0,0,100,0,100,100);
}
void keyPressed(){ useVFlip = !useVFlip; }
void drawAxes(int size){
pushStyle();
strokeWeight(10);
stroke(192,0,0);
line(0,0,size,0);
stroke(0,192,0);
line(0,0,0,size);
popStyle();
}
You could do the same with a PMatrix2D, but not sure how familiar your are with them:
boolean useCustomCS = true;
PMatrix2D customCS;
void setup(){
size(400,400);
customCS = new PMatrix2D( 1, 0, 0,
0, -1,height);
fill(0);
}
void draw(){
background(255);
if(useCustomCS) applyMatrix(customCS);
drawAxes(100);
translate(width * .5, useCustomCS ? height-mouseY : mouseY);
text("real Y:" + mouseY + " flipped Y: " + (height-mouseY),0,0);
triangle(0,0,100,0,100,100);
}
void keyPressed(){ useCustomCS = !useCustomCS; }
void drawAxes(int size){
pushStyle();
strokeWeight(10);
stroke(192,0,0);
line(0,0,size,0);
stroke(0,192,0);
line(0,0,0,size);
popStyle();
}

Answer 2

Try the following:
translate(0,height);
scale(1,-1);