如何加载和优化位图

Question

我用Bitmap包生成了自定义验证码，如何让它生成的图片更大更清晰。这是怎么做到的？再次感谢您的帮助。

enter image description here

我搜索了一些答案，none 似乎有不错的结果

optimizing bitmap loading by using aSyncTask

Answer 1

试试下面的代码，将图片修改为JPEG格式，可以缩小图片大小，比较清晰。

    static void ImgTestTwo()
        {
            string filename = @"E:\CoreWork\backone.jpg";
            string targetname = @"E:\CoreWork\temp1.jpg";


    
        Bitmap bitmap = new Bitmap(filename);
        //Keep the ratio of the image unchanged, zoom the image
        int width = 1000,
            height = 1000;
        if (bitmap.Width > bitmap.Height)
        {
            //Width is large, calculate height
            height = Convert.ToInt32(width * (bitmap.Height * 1.0 / bitmap.Width));
        }
        else
        {
            //height is large, calculate width
            width = Convert.ToInt32(height * (bitmap.Width * 1.0 / bitmap.Height));
        }
        Bitmap result = ResizeImage(bitmap, width, height);
    
        filename = filename.Substring(0,filename.LastIndexOf('.'))+".jpg";
        //Save the picture and specify the save format as Jpeg, which will take up less space
        result.Save(targetname,ImageFormat.Jpeg);
        result.Dispose();
        bitmap.Dispose();
    }
    /// <summary>  
    ///  Resize img
    /// </summary>  
    /// <param name="bmp">original Bitmap </param>  
    /// <param name="newW">new width</param>  
    /// <param name="newH">new heights</param>  
    /// <returns>Process later pictures</returns>  
    public static Bitmap ResizeImage(Bitmap bmp, int newW, int newH)
    {
        try
        {
            Bitmap b = new Bitmap(newW, newH);
            Graphics g = Graphics.FromImage(b);
            // The quality of the interpolation algorithm
            //g.InterpolationMode = InterpolationMode.NearestNeighbor;
            g.DrawImage(bmp, new Rectangle(0, 0, newW, newH), new Rectangle(0, 0, bmp.Width, bmp.Height), GraphicsUnit.Pixel);
            g.Dispose();
            return b;
        }
        catch(Exception ex)
        {
            return null;
        }
    }

如何加载和优化位图

How Bitmap is loaded and optimized

asp.net-core

bitmap