GDI+ 旋转量针

Question

更新我必须根据以下答案使其工作的最终代码：

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+ 规格表。除了针旋转外，我一切正常。我已经阅读了尽可能多的文章，但无法弄清楚如何成功地做到这一点。我可以自己计算角度，但我需要从针图像中的一个点旋转针。 68 像素、39 像素（从左上角开始的 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，并实际围绕原点绘制图像。

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

诀窍是平移坐标系，使您想要的轴心点位于原点，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));
}

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