编程问题 如何用c#实现图片格式转换成png格式

将图片转换成png格式，默认将背景修改成透明

补充：用其他语言也行

答案： private void button1_Click(object sender, EventArgs e)//打开一个图片
        {
            this.openFileDialog1.ShowDialog();
            if (this.openFileDialog1.FileName == "")
            {
                MessageBox.Show("请选择一个文件");
                return;
            }
           
         
               
                    this.pictureBox1.Image = Bitmap.FromFile(this.openFileDialog1.FileName);
        
        private void button2_Click(object sender, EventArgs e)//以另一种格式保存图片
        {
            this.saveFileDialog1.ShowDialog();
            string name = this.saveFileDialog1.FileName;
            if (this.saveFileDialog1.FileName == "")
            {
                MessageBox.Show("请选择一个文件");
            }
            MessageBox.Show(this.saveFileDialog1.FileName);
            if (this.radioButton1.Checked)
            {
                this.pictureBox1.Image.Save(name + ".bmp", System.Drawing.Imaging.ImageFormat.Bmp);
            }
            if (this.radioButton2.Checked)
            {
                this.pictureBox1.Image.Save(name + ".tif", System.Drawing.Imaging.ImageFormat.Tiff);
            } 
            if (this.radioButton3.Checked)
            {
                this.pictureBox1.Image.Save(name + ".Gif", System.Drawing.Imaging.ImageFormat.Gif);
            }
            if (this.radioButton4.Checked)
            {
                this.pictureBox1.Image.Save(name + ".Jpeg", System.Drawing.Imaging.ImageFormat.Jpeg);
            } if (this.radioButton5.Checked)
            {
                this.pictureBox1.Image.Save(name + ".Png", System.Drawing.Imaging.ImageFormat.Png);
            }
            if (this.radioButton6.Checked)
            {
                this.pictureBox1.Image.Save(name + ".Wmf", System.Drawing.Imaging.ImageFormat.Wmf);
            }
        }

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