二次贝塞尔曲线数学 [英] Quadratic bezier curve math

问题描述

有人可以帮我这个忙吗? 当我有这样的贝塞尔曲线时: https://www.w3schools.com/code/tryit.asp?filename= FX0KJBP2EZ3S

Can someone help me with this: When I have a bezier curve like this: https://www.w3schools.com/code/tryit.asp?filename=FX0KJBP2EZ3S

P0(X) = 0 P0(Y) = 50
P1(X) = 100 P1(Y) = 25
P2(X) = 200 P2(Y) = 50

并使贝塞尔曲线变小:

https://www.w3schools.com/code/tryit.asp ?filename = FX0KL478CRY4

由于距离P0.X和P2.X，P1较高.如何保持P1的高度始终保持在同一高度?

the P1 is higher due to the distance P0.X and P2.X. How can I keep the height of P1 so it is allways in the same height?

推荐答案

要按比例缩小曲线(使形状相同但更小)，您必须以相同的比例更改控制点的差异.因此，应将Y1-Y0更改为与(X2'-X0')/(X2-X0):25 / (200/50) = 6.25类似.整数:

To shrink curve proportionally (to make the same form but smaller) you have to change differences of control points in the same ratio. So Y1-Y0 should be changed similar to (X2'-X0')/(X2-X0) : 25 / (200/50) = 6.25. In integers:

ctx.quadraticCurveTo(25, 44, 50, 50);

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