rect from 4 co-ordinates

Programming Questions

stphnmnslw

in Programming Questions • 1 year ago

Hey,

I have 8 co-ordinates that I want to draw a rect around:

x1,y1, x2,y2

x3,y3 x4,y4

i pass x1,y1 into rect:

rect ( x1,y1, width, height )

I need to work out the width and height from the other co-ordinates and I have tried:

width = x2 - x1;
height = y1 - y3;

this doesn't seem to work but I'm not sure what the formula to work this out is...

If anyone has any Ideas I would really appreciate it as I'm stumped!

Replies(7)

asimes

Re: rect from 4 co-ordinates

1 year ago

http://processing.org/reference/rect_.html

x1, y1 is the only coordinate you need to worry about. You make the rect wider from that point with x4-x1 in your case (or x2-x1) and taller with y4-y1 (or y3-y1).

PhiLho

Re: rect from 4 co-ordinates

1 year ago

" this doesn't seem to work"
If you gave a small sketch showing what you do, we could fix it. Here, height seems negative...

amnon.owed

Re: rect from 4 co-ordinates

1 year ago

Just use the CORNERS rectMode().

Then you only need two coordinates (top-left and bottom-right) to specify the rect.

stphnmnslw

Re: rect from 4 co-ordinates

1 year ago

THanks guys using CORNERS works great to draw the rectangle around the area I want... I need to work out the width/ and height (I'm cropping a GLTexture which accepts x,y,width,height so asimes post is useful as well.

Thanks for your help!

stphnmnslw

Re: rect from 4 co-ordinates

1 year ago

I am still getting wierd behaviour,, with my code the box is centered around the first point and I don't know why its acting so strangely: heres my code:

Handle[] handles;
int num;
int[] positions;
void setup()
{
size(200, 300);
num = 4;
handles = new Handle[num];
int squareScale = 10;
for(int i=0; i<num; i++) {
handles[0] = new Handle( 20, 20, squareScale, handles);
handles[1] = new Handle( 20, 100, squareScale, handles);
handles[2] = new Handle( 100, 20, squareScale, handles);
handles[3] = new Handle( 100, 100, squareScale, handles);
// 0 2
//
//
// 1 3
}
}
void draw()
{
smooth();
background(153);
for(int i=0; i<num; i++) {
handles[i].update();
handles[i].display();
handles[0].xPosition = handles[2].xPosition;
handles[1].xPosition = handles[3].xPosition;
handles[0].yPosition = handles[1].yPosition;
handles[2].yPosition = handles[3].yPosition;
float Bwidth = handles[3].xPosition - handles[0].xPosition;
float Bheight = handles[3].yPosition - handles[0].yPosition;
noFill();
stroke(0);
//rectMode(CORNER);
//rect( handles[0].xPosition, handles[0].yPosition, handles[3].xPosition, handles[3].yPosition);
rect(handles[0].xPosition, handles[0].yPosition,Bwidth,Bheight);
}
// fill(0);
}
void mouseReleased()
{
for(int i=0; i<num; i++) {
handles[i].release();
}
}
class Handle
{
int x, y;
int boxx, boxy;
int xPosition, yPosition;
int[] position;
int size;
// over variables
boolean overY, overX, overXY;
// press Variables
boolean pressY, pressX, pressXY;
// locked variables
boolean lockedY = false;
boolean lockedX = false;
boolean lockedXY = false;
boolean otherslocked = false;
Handle[] others;
int blah;
Handle( int iy, int ix, int is, Handle[] o)
{
xPosition = ix;
yPosition = iy;
size = is;
boxx = ix;
boxy = iy;
others = o;
}
int[] update()
{
boxx = xPosition;
boxy = yPosition;
for(int i=0; i<others.length; i++) {
if(others[i].lockedX == true || others[i].lockedY == true || others[i].lockedXY == true) {
otherslocked = true;
break;
}
else {
otherslocked = false;
}
}
if(otherslocked == false) {
overY();
overX();
overXY();
pressY();
pressX();
pressXY();
}
if(pressY) {
yPosition = lock(mouseY+size, size/2, height-size/2-1);
}
if(pressX) {
xPosition = lock(mouseX-size, size/2, width-size/2-1);
}
if(pressXY) {
xPosition = lock(mouseX, size/2, width-size/2-1);
yPosition = lock(mouseY, size/2, height-size/2-1);
}
int[] position = {xPosition,yPosition};
return position;
}
void overY()
{
if(overRectY(boxx, boxy-size, size, size)) {
overY = true;
}
else {
overY = false;
}
}
void overX()
{
if(overRectX(boxx+size, boxy, size, size)) {
overX = true;
}
else {
overX = false;
}
}
void overXY()
{
if(overRectX(boxx, boxy, size, size)) {
overXY = true;
}
else {
overXY = false;
}
}
void pressY()
{
if(overY && mousePressed || lockedY) {
pressY = true;
lockedY = true;
}
else {
pressY = false;
}
}
void pressX()
{
if(overX && mousePressed || lockedX) {
pressX = true;
lockedX = true;
}
else {
pressX = false;
}
}
void pressXY()
{
if(overXY && mousePressed || lockedXY) {
pressXY = true;
lockedXY = true;
}
else {
pressXY = false;
}
}
void release()
{
lockedY = false;
lockedX = false;
lockedXY = false;
}
void display()
{
fill(255);
strokeWeight(1);
rectMode(CENTER);
//x
rect(boxx+size, boxy, size, size);
//y
rect(boxx, boxy-size, size, size);
//XY
rect(boxx, boxy, size, size);
//overY
if(overY || pressY) {
fill(255,0,0);
rect(boxx, boxy-size, size, size);
}
//overX
if(overX || pressX) {
fill(0,0,255);
rect(boxx+size, boxy, size, size);
}
//overXY
if(overXY || pressXY) {
fill(0,255,0);
rect(boxx, boxy, size, size);
}
}
boolean overRectY(int x, int y, int width, int height)
{
if (mouseX >= x-size/2 && mouseX <= (x-size/2)+width &&
mouseY >= y-size/2 && mouseY <= (y-size/2)+height) {
return true;
}
else {
return false;
}
}
boolean overRectX(int x, int y, int width, int height)
{
if (mouseX >= x-size/2 && mouseX <= (x-size/2)+width &&
mouseY >= y-size/2 && mouseY <= (y-size/2)+height) {
return true;
}
else {
return false;
}
}
boolean overRectXY(int x, int y, int width, int height)
{
if (mouseX >= x-size/2 && mouseX <= (x-size/2)+width &&
mouseY >= y-size/2 && mouseY <= (y-size/2)+height) {
return true;
}
else {
return false;
}
}
int lock(int val, int minv, int maxv)
{
blah = min(max(val, minv), maxv);
//println(blah);
return min(max(val, minv), maxv);
}
}

stphnmnslw

Re: rect from 4 co-ordinates

1 year ago

I think the problem is the rectMode() within the class has changed the rect mode globally.. wrapping it in pushStyle() , popStyle() should fix the problem

PhiLho

Re: rect from 4 co-ordinates

1 year ago

Yes, Processing is always working at a global level, with rectMode(), fill(), stroke() and so on.

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