How to get path of Bezier curves with coordinates of decimal value

0
votes

I need to get path of some vector shape which is transformed into Bezier curves. I have a 512x512 px canvas with 350x350 px letter "R" in the middle. I need to export somehow a coordinates of points of Bezier curves.

So I have that canvas with coordinates from 0,0 to 511,511 and some shape in it. But, when I save it as *.svg in the path are for example (M 256.124 373.811 l-85.544 -46.3289 c -21.8516,33.0922 -34.017,54.9238).

I understand that svg coordinate system differs from carthesian system. That real numbers are close to wanted decimal numbers but why there are negative numbers?

But I need coordinates of pixels in decimal format and from range 0,0 to 511,511. For example (M 256 377 C 23 532 123 43 123 352)

Is there a way to get path like that?

1
canvasgraphicscoordinatesbeziercoreldraw
The first & last points on a Bezier curve will always be on the curve, but the middle control point(s) might be well off the curve. The middle control point(s) "influence" the curve rather than being on the curve. Therefore you could easily see control points outside your 512x512 coordinates. No problem with that. – markE

1 Answers

1
votes

I already decoded path in .svg from CorelDraw.

Firstly, Corel and most Graphic editors have carthesian coordinate system (point [0,0] is in bottom-left corner). On the other hand, SVG has different system with start point in top-left corner. From this, when I have canvas with size 512x512 px and place mouse on it, I see a point coordinates are for example [128,312] in the SVG path it will be point [128,200]. See the pictures below.

Carthesian coordinate systemSVG

Next, path continues L-89,8385 -46,3289 C-22,9477,33,0922 -35,7249,54,9238 -38,4096,65,4971. This mean Line to point, which is 89.84 px smaller on the x-axis and 46.33 px smaller on the y-axis. So you basically deduct that numbers from the coordinates of current last point.

Lastly, C mean curve to, exactly cubic Beziér curve. This is quite strange. -22,9477,33,0922 means -22.95 px on x-axis and +33.09 px on y-axis for control point 1. As mentioned it is computed from last point on last curve. Next -35,7249,54,9238 is for control point 2 also computed from last point of last curve NOT from control point 1!! And finally -38,4096,65,4971 belongs to endpoint of current curve. Maybe you noticed that start point of curve is not mentioned. Start point is of course end point of last curve/line/...

To the very ending, you can see something like this in SVG path -1,95237,7,5638 -6,18545,13,9241 -12,7772,19,0808 -6,59057,5,07167 -11,3103,7,65002. These are next curves. There is no letter as L,C,M or any other but that are curves because there was C and no other letter to this point. Than you need to get 3 numbers like -1,95237,7,5638 to get next control point 1, control point 2 and end point.

Hope this will help somebody.