GDI +旋转仪表针

Question

更新 最终代码我必须根据以下答案使其工作：

public static byte[] Test(List<TestRange> ranges, int value)
        {
            var min = ranges.Min(t => t.MinValue);
            var max = ranges.Max(t => t.MaxValue);
            var rangeTotal = max - min;
            var valueAngle = ((((float)value-min) / (float)rangeTotal) * (float)270) + (float)135;
            using (var bmp = new Bitmap(500, 500))
            {
                using (var g = Graphics.FromImage(bmp))
                {
                    g.SmoothingMode = SmoothingMode.AntiAlias;
                    var rec = new Rectangle(0, 0, 500, 500);
                    g.FillPie(new SolidBrush(Color.White), rec, 45, 90);
                    var startDeg = 135f;
                    foreach (var item in ranges.OrderBy(o => o.MinValue))
                    {
                        g.FillPie(new SolidBrush(ColorTranslator.FromHtml(item.Color)), rec, startDeg,
                            ((item.MaxValue - (float) item.MinValue)/rangeTotal)*270);
                        startDeg = startDeg + (((item.MaxValue - (float) item.MinValue)/rangeTotal)*270);
                    }
                    g.FillEllipse(new SolidBrush(Color.White), new Rectangle(100, 100, 300, 300));

                    using (var needle = Graphics.FromImage(bmp))
                    {
                        needle.TranslateTransform(250, 250);
                        needle.RotateTransform(valueAngle);
                        needle.TranslateTransform(-68, -39);
                        needle.DrawImage(Image.FromFile(@"C:\temp\needle.png"), new PointF(0,0));
                    }

                    g.FillRectangle(new SolidBrush(Color.Black), new RectangleF(new PointF(150,375), new SizeF(200,72)));
                    var sf = new StringFormat
                    {
                        Alignment = StringAlignment.Center,
                        LineAlignment = StringAlignment.Center
                    };
                    g.DrawString(value.ToString(), new Font(FontFamily.GenericSansSerif, 40), Brushes.White, new PointF(250, 415), sf);

                }
                using (var ms = new MemoryStream())
                {
                    bmp.Save(ms, ImageFormat.Png);
                    return ms.ToArray();
                }

            }
        }

我正在尝试制作自定义GDI +仪表图表。除旋转针外，我的一切都在工作。我已经阅读了尽可能多的文章但我无法弄清楚如何成功地做到这一点。我可以自己计算角度，但我需要从针图像内的一个点旋转针。 68px，39px（左上角为X，Y）。任何帮助，将不胜感激。这是代码：

public static void Test(List<TestRange> ranges, int value)
        {
            var min = ranges.Min(t => t.MinValue);
            var max = ranges.Max(t => t.MaxValue);
            var rangeTotal = max - min;
            using (var bmp = new Bitmap(500, 500))
            {
                using (var g = Graphics.FromImage(bmp))
                {
                    g.SmoothingMode = SmoothingMode.AntiAlias;
                    var rec = new Rectangle(0, 0, 500, 500);
                    g.FillPie(new SolidBrush(Color.White), rec, 45, 90);
                    var startDeg = 135f;
                    foreach (var item in ranges.OrderBy(o => o.MinValue))
                    {
                        g.FillPie(new SolidBrush(ColorTranslator.FromHtml(item.Color)), rec, startDeg,
                            ((item.MaxValue - (float) item.MinValue)/rangeTotal)*270);
                        startDeg = startDeg + (((item.MaxValue - (float) item.MinValue)/rangeTotal)*270);
                    }
                    g.FillEllipse(new SolidBrush(Color.White), new Rectangle(100, 100, 300, 300));

                    //Needle logic
                    using (var needle = Graphics.FromImage(bmp))
                    {
                        //var m = new Matrix();
                        //m.RotateAt(180, new PointF(68,39));
                        //needle.Transform = m;
                        //needle.TranslateTransform(250, 250);
                        //needle.RotateTransform(180);
                        needle.DrawImage(Image.FromFile(@"C:\temp\needle.png"), new PointF(182, 211));
                    }

                    g.FillRectangle(new SolidBrush(Color.Black), new RectangleF(new PointF(150,375), new SizeF(200,72)));
                    var sf = new StringFormat
                    {
                        Alignment = StringAlignment.Center,
                        LineAlignment = StringAlignment.Center
                    };
                    g.DrawString(value.ToString(), new Font(FontFamily.GenericSansSerif, 40), Brushes.White, new PointF(250, 415), sf);

                }
                bmp.Save("C:\\temp\\Test.png", ImageFormat.Png);
            }
        }

这是它输出的图像：

这是needle.png文件：

Answer 1

您需要将旋转与平移变换相结合，并实际在原点周围绘制图像。

public void DrawImageRotated(Graphics g, Image Image, Point Location, Single Angle)
{
    g.ResetTransform();
    g.RotateTransform(Angle);
    g.TranslateTransform(Location.X, Location.Y, Drawing2D.MatrixOrder.Append);
    g.DrawImageUnscaled(Image, -Image.Width / 2, -Image.Height / 2);
    g.ResetTransform();
}

Answer 2

诀窍是翻译坐标系，使您想要的枢轴点位于原点，然后在0,0处绘制图像：

using (var needle = Graphics.FromImage(bmp))
{
    needle.TranslateTransform(182, 211);
    needle.RotateTransform(angle);
    needle.TranslateTransform(-68, -39);
    needle.DrawImage(Image.FromFile(@"C:\temp\needle.png"), new PointF(0, 0));
}