颜色渐变取中间色(验证通过)

/**
	 * 计算渐变颜色值 ARGB
	 * 
	 * @param fraction
	 *            变化比率 0~1
	 * @param startValue
	 *            初始色值
	 * @param endValue
	 *            结束色值
	 * @return
	 */
	private Integer evaluate(float fraction, Object startValue, Integer endValue) {
		int startInt = (Integer) startValue;
		int startA = (startInt >> 24) & 0xff;
		int startR = (startInt >> 16) & 0xff;
		int startG = (startInt >> 8) & 0xff;
		int startB = startInt & 0xff;
		int endInt = (Integer) endValue;
		int endA = (endInt >> 24) & 0xff;
		int endR = (endInt >> 16) & 0xff;
		int endG = (endInt >> 8) & 0xff;
		int endB = endInt & 0xff;
		return (int) ((startA + (int) (fraction * (endA - startA))) << 24)
				| (int) ((startR + (int) (fraction * (endR - startR))) << 16)
				| (int) ((startG + (int) (fraction * (endG - startG))) << 8)
				| (int) ((startB + (int) (fraction * (endB - startB))));
	}

    Private Sub VScrollBarAdv1_ValueChanged(sender As System.Object, e As System.EventArgs) Handles VScrollBarAdv1.ValueChanged
        Dim pFraction As Single = (VScrollBarAdv1.Value - VScrollBarAdv1.Minimum) / (VScrollBarAdv1.Maximum - VScrollBarAdv1.Minimum)
        Dim pColorEvaluate As Integer = getEvaluateColor(pFraction, ButtonX1.BackColor.ToArgb(), ButtonX2.BackColor.ToArgb)
        ButtonX3.BackColor = Color.FromArgb(pColorEvaluate)
    End Sub
    Private Function getEvaluateColor(ByVal pFraction As Single, ByVal pStartColor As Integer, ByVal pEndColor As Integer) As Integer
        Dim pStartA As Integer = (pStartColor >> 24) And &HFF
        Dim pStartR As Integer = (pStartColor >> 16) And &HFF
        Dim pStartG As Integer = (pStartColor >> 8) And &HFF
        Dim pStartB As Integer = (pStartColor) And &HFF

        Dim pEndA As Integer = (pEndColor >> 24) And &HFF
        Dim pEndR As Integer = (pEndColor >> 16) And &HFF
        Dim pEndG As Integer = (pEndColor >> 8) And &HFF
        Dim pEndB As Integer = (pEndColor) And &HFF

        Return (Convert.ToInt32(pStartA + ((pEndA - pStartA) * pFraction)) << 24) + _
        (Convert.ToInt32(pStartR + ((pEndR - pStartR) * pFraction)) << 16) + _
            (Convert.ToInt32(pStartG + ((pEndG - pStartG) * pFraction)) << 8) + _
                Convert.ToInt32(pStartB + ((pEndB - pStartB) * pFraction))
    End Function