一些建议和几个技巧。
不完全是技巧，只是在多个图形转换到位时加快计算速度的一些方法。
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分而治之：将不同的图形效果和转换拆分为不同的、专门的方法来做一件事。然后以一种使这些方法在需要时可以协同工作的方式进行设计。
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保持简单：当 Graphics 对象需要累积多个转换时，矩阵的堆叠顺序可能会导致误解。预先计算一些通用转换（主要是平移和缩放）更简单（并且不太容易产生奇怪结果），然后让 GDI+ 渲染已经预煮的对象和形状.
这里只使用了Matrix.RotateAt 和Matrix.Multiply。
这里有一些关于矩阵变换的注释：Flip the GraphicsPath
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使用正确的工具：例如，用作画布的面板并不是最佳选择。此控件不是双缓冲的；可以启用此功能，但 Panel 类不用于绘图，而 PictureBox（或非系统平面标签）本身支持它。
这里还有一些注意事项：How to apply a fade transition effect to Images
示例代码显示了 4 种缩放方法，以及生成旋转变换（并排工作，不累积）。
使用枚举器 (private enum ZoomMode) 选择缩放模式：
缩放模式：
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ImageLocation：图像缩放就地执行，将画布上的当前位置保持在固定位置。
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CenterCanvas：在缩放图像时，它仍然位于画布的中心。
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CenterMouse：图像被缩放并平移到画布上当前鼠标位置的中心。
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MouseOffset：图像被缩放和平移以保持由鼠标指针在图像本身上的初始位置确定的相对位置。
您可以注意到，代码简化了所有计算，仅应用相对于定义当前图像边界的 Rectangle 且仅与此形状的位置相关的平移。
仅当计算需要预先确定在鼠标滚轮生成下一个缩放因子之后图像大小将是多少时，才会缩放矩形。
已实现功能的视觉示例：
示例代码：
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canvas 是自定义控件，派生自 PictureBox（您可以在底部找到它的定义）。此控件在代码中添加到表单，here。根据需要进行修改。
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trkRotationAngle 是用于定义 Image 当前旋转的 TrackBar。将此控件添加到设计器中的表单。
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radZoom_CheckedChanged 是用于设置当前缩放模式的所有 RadioButtons 的事件处理程序。这些控件设置的值在其Tag 属性中分配。将这些控件添加到设计器中的表单。
using System.Drawing;
using System.Drawing.Drawing2D;
using System.IO;
using System.Windows.Forms;
public partial class frmZoomPaint : Form
{
private float rotationAngle = 0.0f;
private float zoomFactor = 1.0f;
private float zoomStep = .05f;
private RectangleF imageRect = RectangleF.Empty;
private PointF imageLocation = PointF.Empty;
private PointF mouseLocation = PointF.Empty;
private Bitmap drawingImage = null;
private PictureBoxEx canvas = null;
private ZoomMode zoomMode = ZoomMode.ImageLocation;
private enum ZoomMode
{
ImageLocation,
CenterCanvas,
CenterMouse,
MouseOffset
}
public frmZoomPaint()
{
InitializeComponent();
string imagePath = [Path of the Image];
drawingImage = (Bitmap)Image.FromStream(new MemoryStream(File.ReadAllBytes(imagePath)));
imageRect = new RectangleF(Point.Empty, drawingImage.Size);
canvas = new PictureBoxEx(new Size(555, 300));
canvas.Location = new Point(10, 10);
canvas.MouseWheel += canvas_MouseWheel;
canvas.MouseMove += canvas_MouseMove;
canvas.MouseDown += canvas_MouseDown;
canvas.MouseUp += canvas_MouseUp;
canvas.Paint += canvas_Paint;
Controls.Add(canvas);
}
private void canvas_MouseWheel(object sender, MouseEventArgs e)
{
mouseLocation = e.Location;
float zoomCurrent = zoomFactor;
zoomFactor += e.Delta > 0 ? zoomStep : -zoomStep;
if (zoomFactor < .10f) zoomStep = .01f;
if (zoomFactor >= .10f) zoomStep = .05f;
if (zoomFactor < .0f) zoomFactor = zoomStep;
switch (zoomMode) {
case ZoomMode.CenterCanvas:
imageRect = CenterScaledRectangleOnCanvas(imageRect, canvas.ClientRectangle);
break;
case ZoomMode.CenterMouse:
imageRect = CenterScaledRectangleOnMousePosition(imageRect, e.Location);
break;
case ZoomMode.MouseOffset:
imageRect = OffsetScaledRectangleOnMousePosition(imageRect, zoomCurrent, e.Location);
break;
default:
break;
}
canvas.Invalidate();
}
private void canvas_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button != MouseButtons.Left) return;
mouseLocation = e.Location;
imageLocation = imageRect.Location;
canvas.Cursor = Cursors.NoMove2D;
}
private void canvas_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button != MouseButtons.Left) return;
imageRect.Location =
new PointF(imageLocation.X + (e.Location.X - mouseLocation.X),
imageLocation.Y + (e.Location.Y - mouseLocation.Y));
canvas.Invalidate();
}
private void canvas_MouseUp(object sender, MouseEventArgs e) =>
canvas.Cursor = Cursors.Default;
private void canvas_Paint(object sender, PaintEventArgs e)
{
var drawingRect = GetDrawingImageRect(imageRect);
using (var mxRotation = new Matrix())
using (var mxTransform = new Matrix()) {
e.Graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
e.Graphics.PixelOffsetMode = PixelOffsetMode.Half;
mxRotation.RotateAt(rotationAngle, GetDrawingImageCenterPoint(drawingRect));
mxTransform.Multiply(mxRotation);
e.Graphics.Transform = mxTransform;
e.Graphics.DrawImage(drawingImage, drawingRect);
}
}
private void trkRotationAngle_ValueChanged(object sender, EventArgs e)
{
rotationAngle = trkAngle.Value;
canvas.Invalidate();
canvas.Focus();
}
private void radZoom_CheckedChanged(object sender, EventArgs e)
{
var rad = sender as RadioButton;
if (rad.Checked) {
zoomMode = (ZoomMode)int.Parse(rad.Tag.ToString());
}
canvas.Focus();
}
#region Drawing Methods
public RectangleF GetScaledRect(RectangleF rect, float scaleFactor) =>
new RectangleF(rect.Location,
new SizeF(rect.Width * scaleFactor, rect.Height * scaleFactor));
public RectangleF GetDrawingImageRect(RectangleF rect) =>
GetScaledRect(rect, zoomFactor);
public PointF GetDrawingImageCenterPoint(RectangleF rect) =>
new PointF(rect.X + rect.Width / 2, rect.Y + rect.Height / 2);
public RectangleF CenterScaledRectangleOnCanvas(RectangleF rect, RectangleF canvas)
{
var scaled = GetScaledRect(rect, zoomFactor);
rect.Location = new PointF((canvas.Width - scaled.Width) / 2,
(canvas.Height - scaled.Height) / 2);
return rect;
}
public RectangleF CenterScaledRectangleOnMousePosition(RectangleF rect, PointF mousePosition)
{
var scaled = GetScaledRect(rect, zoomFactor);
rect.Location = new PointF(mousePosition.X - (scaled.Width / 2),
mousePosition.Y - (scaled.Height / 2));
return rect;
}
public RectangleF OffsetScaledRectangleOnMousePosition(RectangleF rect, float currentZoom, PointF mousePosition)
{
var currentRect = GetScaledRect(imageRect, currentZoom);
if (!currentRect.Contains(mousePosition)) return rect;
float scaleRatio = currentRect.Width / GetScaledRect(rect, zoomFactor).Width;
PointF mouseOffset = new PointF(mousePosition.X - rect.X, mousePosition.Y - rect.Y);
PointF scaledOffset = new PointF(mouseOffset.X / scaleRatio, mouseOffset.Y / scaleRatio);
PointF position = new PointF(rect.X - (scaledOffset.X - mouseOffset.X),
rect.Y - (scaledOffset.Y - mouseOffset.Y));
rect.Location = position;
return rect;
}
#endregion
}
简单的PictureBoxEx 自定义控件（根据需要进行修改和扩展）：
此 PictureBox 是可选的，因此可以通过鼠标单击获得焦点
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;
[DesignerCategory("Code")]
public class PictureBoxEx : PictureBox
{
public PictureBoxEx() : this (new Size(200, 200)){ }
public PictureBoxEx(Size size) {
SetStyle(ControlStyles.Selectable | ControlStyles.UserMouse, true);
BorderStyle = BorderStyle.FixedSingle;
Size = size;
}
}