c# - SetPixel 太慢了。有没有更快的方法来绘制位图？

Question

我正在开发一个小型绘图程序。我在位图上使用 SetPixel 来绘制线条。当画笔尺寸变大时，例如 25 像素，性能会明显下降。我想知道是否有更快的方法来绘制位图。以下是该项目的一些背景:

• 我使用位图是为了可以利用图层，例如在 Photoshop 或 The GIMP 中。
• 线条是手动绘制的，因为这最终会使用绘图板压力来改变线条长度的大小。
• 线条最终应该沿边缘消除锯齿/平滑。

我将包括我的绘图代码以防万一它是缓慢的而不是 Set-Pixel 位。

这是在绘画发生的窗口中:

    private void canvas_MouseMove(object sender, MouseEventArgs e)
    {
        m_lastPosition = m_currentPosition;
        m_currentPosition = e.Location;

        if(m_penDown && m_pointInWindow)
            m_currentTool.MouseMove(m_lastPosition, m_currentPosition, m_layer);
        canvas.Invalidate();
    }

---

MouseMove 的实现:

    public override void MouseMove(Point lastPos, Point currentPos, Layer currentLayer)
    {
        DrawLine(lastPos, currentPos, currentLayer);
    }

---

画线的实现:

    // The primary drawing code for most tools. A line is drawn from the last position to the current position
    public override void DrawLine(Point lastPos, Point currentPos, Layer currentLayer)
    {
        // Creat a line vector
        Vector2D vector = new Vector2D(currentPos.X - lastPos.X, currentPos.Y - lastPos.Y);

        // Create the point to draw at
        PointF drawPoint = new Point(lastPos.X, lastPos.Y);

        // Get the amount to step each time
        PointF step = vector.GetNormalisedVector();

        // Find the length of the line
        double length = vector.GetMagnitude();

        // For each step along the line...
        for (int i = 0; i < length; i++)
        {
            // Draw a pixel
            PaintPoint(currentLayer, new Point((int)drawPoint.X, (int)drawPoint.Y));
            drawPoint.X += step.X;
            drawPoint.Y += step.Y;
        }
    }

---

PaintPoint 的实现:

    public override void PaintPoint(Layer layer, Point position)
    {
        // Rasterise the pencil tool

        // Assume it is square

        // Check the pixel to be set is witin the bounds of the layer

            // Set the tool size rect to the locate on of the point to be painted
        m_toolArea.Location = position;

            // Get the area to be painted
        Rectangle areaToPaint = new Rectangle();
        areaToPaint = Rectangle.Intersect(layer.GetRectangle(), m_toolArea);

            // Check this is not a null area
        if (!areaToPaint.IsEmpty)
        {
            // Go through the draw area and set the pixels as they should be
            for (int y = areaToPaint.Top; y < areaToPaint.Bottom; y++)
            {
                for (int x = areaToPaint.Left; x < areaToPaint.Right; x++)
                {
                    layer.GetBitmap().SetPixel(x, y, m_colour);
                }
            }
        }
    }

非常感谢您提供的任何帮助。

Answer 1

您可以锁定位图数据并使用指针手动设置值。它要快得多。尽管您将不得不使用不安全的代码。

public override void PaintPoint(Layer layer, Point position)
    {
        // Rasterise the pencil tool

        // Assume it is square

        // Check the pixel to be set is witin the bounds of the layer

        // Set the tool size rect to the locate on of the point to be painted
        m_toolArea.Location = position;

        // Get the area to be painted
        Rectangle areaToPaint = new Rectangle();
        areaToPaint = Rectangle.Intersect(layer.GetRectangle(), m_toolArea);

        Bitmap bmp;
        BitmapData data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
        int stride = data.Stride;
        unsafe
        {
            byte* ptr = (byte*)data.Scan0;
            // Check this is not a null area
            if (!areaToPaint.IsEmpty)
            {
                // Go through the draw area and set the pixels as they should be
                for (int y = areaToPaint.Top; y < areaToPaint.Bottom; y++)
                {
                    for (int x = areaToPaint.Left; x < areaToPaint.Right; x++)
                    {
                        // layer.GetBitmap().SetPixel(x, y, m_colour);
                        ptr[(x * 3) + y * stride] = m_colour.B;
                        ptr[(x * 3) + y * stride + 1] = m_colour.G;
                        ptr[(x * 3) + y * stride + 2] = m_colour.R;
                    }
                }
            }
        }
        bmp.UnlockBits(data);
    }