我正在为Android创建一个像素艺术编辑器，最近我使用中点椭圆算法实现了一个椭圆工具。
我只想强调这个工具工作 * 完美！*
唯一的问题是，如果我在一个更大的位图（大约1000 x1000或更大）上绘制一个大椭圆，椭圆的边会被剪切，并且会出现一些奇怪的行为：

为什么会这样呢？
中点椭圆算法的代码：

package com.therealbluepandabear.pixapencil.algorithms

import com.therealbluepandabear.pixapencil.activities.canvas.canvascommands.overrideSetPixel
import com.therealbluepandabear.pixapencil.models.Coordinates

class MidpointEllipseAlgorithm(private val algorithmInfo: AlgorithmInfoParameter, private val xDEC: Boolean = false, private val yDEC: Boolean = false, private val filledMode: Boolean = false) {
    private val shouldLineIgnoreBrush = true

    private fun putPixel(p1: Coordinates, p2: Coordinates) {
        val xc = p1.x
        val yc = p1.y

        val x = p2.x
        val y = p2.y

        if (!xDEC && !yDEC) {
            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates(xc + x, yc + y),
                algorithmInfo.color
            )

            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates(xc + x, yc - y),
                algorithmInfo.color
            )

            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates(xc - x, yc - y),
                algorithmInfo.color
            )

            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates(xc - x, yc + y),
                algorithmInfo.color
            )

            if (filledMode) {
                val lineAlgorithmInstance = LineAlgorithm(algorithmInfo, shouldLineIgnoreBrush)

                lineAlgorithmInstance.compute(
                    Coordinates(xc + x, yc + y),
                    Coordinates(xc + x, yc - y),
                )

                lineAlgorithmInstance.compute(
                    Coordinates(xc - x, yc - y),
                    Coordinates(xc - x, yc + y),
                )
            }
        } else if (xDEC && !yDEC) {
            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates((xc + x) + 1, yc + y),
                algorithmInfo.color
            )

            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates((xc + x) + 1, yc - y),
                algorithmInfo.color
            )

            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates(xc - x, yc - y),
                algorithmInfo.color
            )

            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates(xc - x, yc + y),
                algorithmInfo.color
            )

            if (filledMode) {
                val lineAlgorithmInstance = LineAlgorithm(algorithmInfo, shouldLineIgnoreBrush)

                lineAlgorithmInstance.compute(
                    Coordinates((xc + x) + 1, yc + y),
                    Coordinates((xc + x) + 1, yc - y),
                )

                lineAlgorithmInstance.compute(
                    Coordinates(xc - x, yc - y),
                    Coordinates(xc - x, yc + y),
                )
            }
        } else if (!xDEC && yDEC) {
            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates(xc + x, (yc + y) + 1),
                algorithmInfo.color
            )

            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates(xc + x, yc - y),
                algorithmInfo.color
            )

            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates(xc - x, yc - y),
                algorithmInfo.color
            )

            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates(xc - x, (yc + y) + 1),
                algorithmInfo.color
            )

            if (filledMode) {
                val lineAlgorithmInstance = LineAlgorithm(algorithmInfo, shouldLineIgnoreBrush)

                lineAlgorithmInstance.compute(
                    Coordinates(xc + x, (yc + y) + 1),
                    Coordinates(xc + x, yc - y),
                )

                lineAlgorithmInstance.compute(
                    Coordinates(xc - x, yc - y),
                    Coordinates(xc - x, (yc + y) + 1),
                )
            }
        } else {
            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates((xc + x) + 1, (yc + y) + 1),
                algorithmInfo.color
            )

            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates((xc + x) + 1, yc - y),
                algorithmInfo.color
            )

            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates(xc - x, yc - y),
                algorithmInfo.color
            )

            algorithmInfo.canvasCommandsHelperInstance.overrideSetPixel(
                Coordinates(xc - x, (yc + y) + 1),
                algorithmInfo.color
            )

            if (filledMode) {
                val lineAlgorithmInstance = LineAlgorithm(algorithmInfo, shouldLineIgnoreBrush)

                lineAlgorithmInstance.compute(
                    Coordinates((xc + x) + 1, (yc + y) + 1),
                    Coordinates((xc + x) + 1, yc - y),
                )

                lineAlgorithmInstance.compute(
                    Coordinates(xc - x, yc - y),
                    Coordinates(xc - x, (yc + y) + 1),
                )
            }
        }
    }

    fun compute(p1: Coordinates, rx: Int, ry: Int) {
        val idp = Coordinates(0, ry)

        var xkp1 = idp.x
        var ykp1 = idp.y

        var lxkp1: Int
        var lykp1: Int

        var p1k = (ry * ry) + ((rx * rx) / 4) - (ry * (rx * rx))

        val incy = p1.y
        val incx = p1.x

        putPixel(Coordinates(incx, incy), Coordinates(xkp1, ykp1))

        while (
            (2 * (xkp1 + 1) * (ry * ry))
            <
            (2 * ykp1 * (rx * rx))
        ) {
            p1k += if (p1k >= 0) {
                xkp1++
                ykp1--

                lxkp1 = xkp1 - 1
                lykp1 = ykp1 + 1

                (ry * ry) + (2 * (lxkp1 + 1)) * (ry * ry) + (rx * rx) * ((ykp1 * ykp1) - (lykp1 * lykp1)) - (rx * rx) * (ykp1 - lykp1)
            } else {
                xkp1++

                lxkp1 = xkp1 - 1
                lykp1 = ykp1

                (ry * ry) + (2 * (lxkp1 + 1)) * (ry * ry) + (rx * rx) * ((ykp1 * ykp1) - (lykp1 * lykp1))
            }

            putPixel(Coordinates(incx, incy), Coordinates(xkp1, ykp1))
        }

        var p2k = (ry * ry) * ((xkp1 + 0.5) * (xkp1 + 0.5)) + (rx * rx) * ((ykp1 - 1) * (ykp1 - 1)) - ((rx * rx) * (ry * ry))

        while (
            ykp1 > 0
        ) {
            if (p2k >= 0) {
                ykp1--
                lykp1 = ykp1 + 1
                lxkp1 = xkp1

                p2k += (rx * rx) - 2 * (rx * rx) * (lykp1 - 1) + (ry * ry) * ((xkp1 * xkp1) - (lxkp1 * lxkp1))
            } else {
                xkp1++
                lxkp1 = xkp1 - 1
                ykp1--
                lykp1 = ykp1 + 1

                p2k += (rx * rx) - 2 * (rx * rx) * (lykp1 - 1) + (ry * ry) * ((xkp1 * xkp1) - (lxkp1 * lxkp1)) + (ry * ry) * (xkp1 - lxkp1)
            }

            putPixel(Coordinates(incx, incy), Coordinates(xkp1, ykp1))
        }
    }
}

这个问题只存在于MidpointEllipseAlgorithm中，所以它已经被隔离了。overrideSetPixel函数没有导致这个行为，因为当我用一个简单的Bitmap.setPixel替换它时，问题仍然存在。但是，尽管它已经被隔离了，我还是不明白为什么会发生这种情况。
如果你在较小的画布上画椭圆，这个行为就不会被演示，它可以完美地工作。只有当你在一个大的位图上画一个足够大的椭圆时，这个行为才会被演示。
为什么在大的位图上它会被这样“剪切”？这完全是无稽之谈，因为算法本身已经被我的同行审查过了，而且它是高标准的。我试图通过调整变量和不等式来修复它，但我不知道它是从哪里来的，我甚至把我的算法代码与网上的算法代码进行了比较，即使我替换了它，我仍然会遇到这个问题。