C#怎么用滚轮实现picturebox里的图片的放大和缩小

Question

比如滚轮向前推是缩小，向后推是放大，类似这样的。
是picturebox里图片的放大的缩小，不是控件放大和缩小

Answer 1

public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

    private Image sourceImage = null;
    private int imageWidth = 0;
    private int imageHeight = 0;
    private float zoom = 1;
    private const float reduce = 0.1f;
    private const float enlarge = 1f;

    private void Form1_Load(object sender, EventArgs e)
    {
        sourceImage = ZoomImage.Properties.Resources._123456;
        imageWidth = sourceImage.Width;
        imageHeight = sourceImage.Height;
        pictureBox1.MouseWheel += pictureBox1_MouseWheel;
    }

    private 
    void pictureBox1_MouseWheel(object sender, MouseEventArgs e)
    {
        if (e.Delta > 0)
        {
            if (zoom > 1)
            {
                zoom -= enlarge;
            }
            else
            {
                zoom -= reduce;
            }
            if (zoom >= 10)
            {
                zoom = 10;
            }
            if (zoom <= 0)
            {
                zoom = 0.1f;
            }
        }
        else
        {
            if (zoom > 1)
            {
                zoom += enlarge;
            }
            else
            {
                zoom += reduce;
            }
            if (zoom >= 10)
            {
                zoom = 10;
            }
            if (zoom <= 0)
            {
                zoom = 0.1f;
            }
        }

        pictureBox1.Image = ZoomImageMethod((Image)ZoomImage.Properties.Resources._123456, Convert.ToInt32(Math.Ceiling(imageWidth * zoom)), Convert.ToInt32(Math.Ceiling(imageHeight * zoom)));
    }

    private Image ZoomImageMethod(Image bitmap, int destHeight, int destWidth)
    {
        try
        {
            System.Drawing.Image sourImage = bitmap;
            int width = 0, height = 0;
            //按比例缩放             
            int sourWidth = sourImage.Width;
            int sourHeight = sourImage.Height;
            if (sourHeight > destHeight || sourWidth > destWidth)
            {
                if (sourHeight / (destHeight * 1.0) > sourWidth / (destWidth * 1.0))
                {
                    height = destHeight;
                    width = Convert.ToInt32(Math.Floor(sourWidth * destHeight / (sourHeight * 1.0)));
                }
                else
                {
                    width = destWidth;
                    height = Convert.ToInt32(Math.Floor(sourHeight * destWidth / (sourWidth * 1.0)));
                }
            }
            else
            {
                width = sourWidth;
                height = sourHeight;
            }
            Bitmap destBitmap = new Bitmap(destWidth, destHeight);
            Graphics g = Graphics.FromImage(destBitmap);
            g.Clear(Color.White);
            //设置画布的描绘质量           
            g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
            g.DrawImage(sourImage, new Rectangle((destWidth - width) / 2, (destHeight - height) / 2, width, height), 0, 0, sourImage.Width, sourImage.Height, GraphicsUnit.Pixel);
            g.Dispose();
            //设置压缩质量       
            System.Drawing.Imaging.EncoderParameters encoderParams = new System.Drawing.Imaging.EncoderParameters();
            long[] quality = new long[1];
            quality[0] = 100;
            System.Drawing.Imaging.EncoderParameter encoderParam = new System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality);
            encoderParams.Param[0] = encoderParam;
            sourImage.Dispose();
            return destBitmap;
        }
        catch
        {
            return bitmap;
        }
    }
}