Draw rectangle on mousedown event
I have a basic zoomable and pannable canvas build in Fabric.js. I need to draw a rectangle on every mousedown event at the clicked coordinate position. The problem happens when the canvas is transformed from it's initial state - the drawing is not accurate because the coordinates must be transformed with the new matrix.
How can I transform the coordinates from the mouse event using the new matrix?
Here is the code I am using. Thanks
canvas.on('mouse:down', function (opt) {
const evt = opt.e;
const p = new fabric.Rect({
left: opt.e.offsetX,
top: opt.e.offsetY,
fill: 'red',
width: 30,
height: 30,
});
canvas.add(p);
});
Update 1: I found a method to transform points (fabric.util.transformPoint()), but
the transformed points were not correct according to the canvas context.
const evt = opt.e;
const point = new fabric.Point(opt.e.offsetX, opt.e.offsetY);
const transformedPoint = fabric.util.transformPoint(point, this.viewportTransform);
const p = new fabric.Rect({
left: transformedPoint.x,
top: transformedPoint.y,
fill: 'red',
width: 30,
height: 30,
});
this.add(p);
javascript html5-canvas fabricjs
asked Nov 19 '18 at 20:58
xepexepe
5016
add a comment |
I have a basic zoomable and pannable canvas build in Fabric.js. I need to draw a rectangle on every mousedown event at the clicked coordinate position. The problem happens when the canvas is transformed from it's initial state - the drawing is not accurate because the coordinates must be transformed with the new matrix.
How can I transform the coordinates from the mouse event using the new matrix?
Here is the code I am using. Thanks
canvas.on('mouse:down', function (opt) {
const evt = opt.e;
const p = new fabric.Rect({
left: opt.e.offsetX,
top: opt.e.offsetY,
fill: 'red',
width: 30,
height: 30,
});
canvas.add(p);
});
Update 1: I found a method to transform points (fabric.util.transformPoint()), but
the transformed points were not correct according to the canvas context.
const evt = opt.e;
const point = new fabric.Point(opt.e.offsetX, opt.e.offsetY);
const transformedPoint = fabric.util.transformPoint(point, this.viewportTransform);
const p = new fabric.Rect({
left: transformedPoint.x,
top: transformedPoint.y,
fill: 'red',
width: 30,
height: 30,
});
this.add(p);
javascript html5-canvas fabricjs
asked Nov 19 '18 at 20:58
xepexepe
5016
What do you mean by 'it isn't working for me'?
– Konowy
Nov 19 '18 at 23:32
Sorry, I meant that the transformed points were not correct according to the canvas context (using fabric.util.transformPoint())
– xepe
Nov 20 '18 at 9:15
add a comment |
I have a basic zoomable and pannable canvas build in Fabric.js. I need to draw a rectangle on every mousedown event at the clicked coordinate position. The problem happens when the canvas is transformed from it's initial state - the drawing is not accurate because the coordinates must be transformed with the new matrix.
How can I transform the coordinates from the mouse event using the new matrix?
Here is the code I am using. Thanks
canvas.on('mouse:down', function (opt) {
const evt = opt.e;
const p = new fabric.Rect({
left: opt.e.offsetX,
top: opt.e.offsetY,
fill: 'red',
width: 30,
height: 30,
});
canvas.add(p);
});
Update 1: I found a method to transform points (fabric.util.transformPoint()), but
the transformed points were not correct according to the canvas context.
const evt = opt.e;
const point = new fabric.Point(opt.e.offsetX, opt.e.offsetY);
const transformedPoint = fabric.util.transformPoint(point, this.viewportTransform);
const p = new fabric.Rect({
left: transformedPoint.x,
top: transformedPoint.y,
fill: 'red',
width: 30,
height: 30,
});
this.add(p);
javascript html5-canvas fabricjs
asked Nov 19 '18 at 20:58
xepexepe
5016
I have a basic zoomable and pannable canvas build in Fabric.js. I need to draw a rectangle on every mousedown event at the clicked coordinate position. The problem happens when the canvas is transformed from it's initial state - the drawing is not accurate because the coordinates must be transformed with the new matrix.
How can I transform the coordinates from the mouse event using the new matrix?
Here is the code I am using. Thanks
canvas.on('mouse:down', function (opt) {
const evt = opt.e;
const p = new fabric.Rect({
left: opt.e.offsetX,
top: opt.e.offsetY,
fill: 'red',
width: 30,
height: 30,
});
canvas.add(p);
});
Update 1: I found a method to transform points (fabric.util.transformPoint()), but
the transformed points were not correct according to the canvas context.
const evt = opt.e;
const point = new fabric.Point(opt.e.offsetX, opt.e.offsetY);
const transformedPoint = fabric.util.transformPoint(point, this.viewportTransform);
const p = new fabric.Rect({
left: transformedPoint.x,
top: transformedPoint.y,
fill: 'red',
width: 30,
height: 30,
});
this.add(p);
javascript html5-canvas fabricjs
javascript html5-canvas fabricjs
asked Nov 19 '18 at 20:58
xepexepe
5016
asked Nov 19 '18 at 20:58
xepexepe
5016
edited Nov 20 '18 at 9:28
xepe
asked Nov 19 '18 at 20:58
xepexepe
5016
asked Nov 19 '18 at 20:58
xepexepe
5016
asked Nov 19 '18 at 20:58
xepexepe
5016
5016
What do you mean by 'it isn't working for me'?
– Konowy
Nov 19 '18 at 23:32
Sorry, I meant that the transformed points were not correct according to the canvas context (using fabric.util.transformPoint())
– xepe
Nov 20 '18 at 9:15
add a comment |
What do you mean by 'it isn't working for me'?
– Konowy
Nov 19 '18 at 23:32
Sorry, I meant that the transformed points were not correct according to the canvas context (using fabric.util.transformPoint())
– xepe
Nov 20 '18 at 9:15
What do you mean by 'it isn't working for me'?
– Konowy
Nov 19 '18 at 23:32
What do you mean by 'it isn't working for me'?
– Konowy
Nov 19 '18 at 23:32
Sorry, I meant that the transformed points were not correct according to the canvas context (using fabric.util.transformPoint())
– xepe
Nov 20 '18 at 9:15
Sorry, I meant that the transformed points were not correct according to the canvas context (using fabric.util.transformPoint())
– xepe
Nov 20 '18 at 9:15
add a comment |
1 Answer
1
active
oldest
votes
I finally solved it using fabric.util.transformPoint() using an inverted matrix. Here is the code for transforming a point in the canvas to a point in the canvas context.
const point = new fabric.Point(offsetX, offsetY);
const invertedMatrix = fabric.util.invertTransform(canvas.viewportTransform)
const transformedPoint = fabric.util.transformPoint(point, invertedMatrix);
answered Nov 20 '18 at 9:22
xepexepe
5016
add a comment |
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1 Answer
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1 Answer
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active
oldest
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oldest
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oldest
votes
I finally solved it using fabric.util.transformPoint() using an inverted matrix. Here is the code for transforming a point in the canvas to a point in the canvas context.
const point = new fabric.Point(offsetX, offsetY);
const invertedMatrix = fabric.util.invertTransform(canvas.viewportTransform)
const transformedPoint = fabric.util.transformPoint(point, invertedMatrix);
answered Nov 20 '18 at 9:22
xepexepe
5016
add a comment |
I finally solved it using fabric.util.transformPoint() using an inverted matrix. Here is the code for transforming a point in the canvas to a point in the canvas context.
const point = new fabric.Point(offsetX, offsetY);
const invertedMatrix = fabric.util.invertTransform(canvas.viewportTransform)
const transformedPoint = fabric.util.transformPoint(point, invertedMatrix);
answered Nov 20 '18 at 9:22
xepexepe
5016
add a comment |
I finally solved it using fabric.util.transformPoint() using an inverted matrix. Here is the code for transforming a point in the canvas to a point in the canvas context.
const point = new fabric.Point(offsetX, offsetY);
const invertedMatrix = fabric.util.invertTransform(canvas.viewportTransform)
const transformedPoint = fabric.util.transformPoint(point, invertedMatrix);
answered Nov 20 '18 at 9:22
xepexepe
5016
I finally solved it using fabric.util.transformPoint() using an inverted matrix. Here is the code for transforming a point in the canvas to a point in the canvas context.
const point = new fabric.Point(offsetX, offsetY);
const invertedMatrix = fabric.util.invertTransform(canvas.viewportTransform)
const transformedPoint = fabric.util.transformPoint(point, invertedMatrix);
answered Nov 20 '18 at 9:22
xepexepe
5016
answered Nov 20 '18 at 9:22
xepexepe
5016
answered Nov 20 '18 at 9:22
xepexepe
5016
answered Nov 20 '18 at 9:22
xepexepe
5016
5016
add a comment |
add a comment |
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What do you mean by 'it isn't working for me'?
– Konowy
Nov 19 '18 at 23:32
Sorry, I meant that the transformed points were not correct according to the canvas context (using fabric.util.transformPoint())
– xepe
Nov 20 '18 at 9:15