C# 如何在运行时从文本动态生成图像

How to generate an image from text on fly at runtime

提问by Ravia

Can anyone guide how to generate image from input text. Image might have any extension doesn't matter.

任何人都可以指导如何从输入文本生成图像。图像可能有任何扩展名都没有关系。

采纳答案by Alistair Evans

Ok, assuming you want to draw a string on an image in C#, you are going to need to use the System.Drawing namespace here:

好的，假设您想在 C# 中的图像上绘制一个字符串，您将需要在此处使用 System.Drawing 命名空间：

private Image DrawText(String text, Font font, Color textColor, Color backColor)
{
    //first, create a dummy bitmap just to get a graphics object
    Image img = new Bitmap(1, 1);
    Graphics drawing = Graphics.FromImage(img);

    //measure the string to see how big the image needs to be
    SizeF textSize = drawing.MeasureString(text, font);

    //free up the dummy image and old graphics object
    img.Dispose();
    drawing.Dispose();

    //create a new image of the right size
    img = new Bitmap((int) textSize.Width, (int)textSize.Height);

    drawing = Graphics.FromImage(img);

    //paint the background
    drawing.Clear(backColor);

    //create a brush for the text
    Brush textBrush = new SolidBrush(textColor);

    drawing.DrawString(text, font, textBrush, 0, 0);

    drawing.Save();

    textBrush.Dispose();
    drawing.Dispose();

    return img;

}

This code will measure the string first, and then create an image of the correct size.

此代码将首先测量字符串，然后创建正确大小的图像。

If you want to save the return of this function, just call the Save method of the returned image.

如果要保存这个函数的返回值，只需调用返回图像的Save方法即可。

回答by Toad

use imagemagickfor rendering text on images (on the server)

使用imagemagick在图像上渲染文本（在服务器上）

Since you are in C# you could also use the .Net classes for bitmap and font manipulation directly (with the classes like: System.Drawing.Bitmapand System.Drawing.Graphics)

由于您使用的是 C#，您还可以直接使用 .Net 类进行位图和字体操作（使用类，例如：System.Drawing.Bitmap和System.Drawing.Graphics）

回答by Freddy

I just translated this method mentioned in this answerto a VB.NET method. Maybe this helps someone.

我只是将这个答案中提到的这个方法翻译成一个 VB.NET 方法。也许这对某人有帮助。

Public Function DrawText(ByVal text As String, ByRef font As   Font, ByRef textColor As Color, ByRef backColor As Color) As Image
    ' first, create a dummy bitmap just to get a graphics object
    Dim img As Image = New Bitmap(1, 1)
    Dim drawing As Graphics = Graphics.FromImage(img)

    ' measure the string to see how big the image needs to be
    Dim textSize As SizeF = drawing.MeasureString(Text, Font)

    ' free up the dummy image and old graphics object
    img.Dispose()
    drawing.Dispose()

    ' create a new image of the right size
    img = New Bitmap(CType(textSize.Width, Integer), CType(textSize.Height, Integer))

    drawing = Graphics.FromImage(img)

    ' paint the background
    drawing.Clear(BackColor)

    ' create a brush for the text
    Dim textBrush As Brush = New SolidBrush(textColor)

    drawing.DrawString(text, font, textBrush, 0, 0)

    drawing.Save()

    textBrush.Dispose()
    drawing.Dispose()

    Return img

End Function

Edit: Fixed typo.

编辑：修正错字。

回答by Dzmitry Lahoda

F#version:

F#版本：

open System.Drawing

let drawText text font textColor backColor =
    let size =
      use dummyImg = new Bitmap(1, 1)
      use drawing = Graphics.FromImage(dummyImg)
      drawing.MeasureString(text, font)
    let img = new Bitmap((int size.Width), (int size.Height))
    use drawing = Graphics.FromImage(img)
    use textBrush = new SolidBrush(textColor)
    do 
      drawing.Clear(backColor)
      drawing.DrawString(text, font, textBrush, PointF())
      drawing.Save() |> ignore
    img

回答by Panayiotis Panayiotou

Thanks Kazar. A slight improvement of the previous answer to use USING for the dispose of the image/graphic objects after used and the introduction of min size param

谢谢卡扎尔。对使用 USING 处理使用后的图像/图形对象的先前答案略有改进，并引入了最小尺寸参数

    private Image DrawTextImage(String currencyCode, Font font, Color textColor, Color backColor) {
        return DrawTextImage(currencyCode, font, textColor, backColor, Size.Empty);
    }
    private Image DrawTextImage(String currencyCode, Font font, Color textColor, Color backColor, Size minSize) {
        //first, create a dummy bitmap just to get a graphics object
        SizeF textSize;
        using (Image img = new Bitmap(1, 1)) {
            using (Graphics drawing = Graphics.FromImage(img)) {
                //measure the string to see how big the image needs to be
                textSize = drawing.MeasureString(currencyCode, font);
                if (!minSize.IsEmpty) {
                    textSize.Width = textSize.Width > minSize.Width ? textSize.Width : minSize.Width;
                    textSize.Height = textSize.Height > minSize.Height ? textSize.Height : minSize.Height;
                }
            }
        }

        //create a new image of the right size
        Image retImg = new Bitmap((int)textSize.Width, (int)textSize.Height);
        using (var drawing = Graphics.FromImage(retImg)) {
            //paint the background
            drawing.Clear(backColor);

            //create a brush for the text
            using (Brush textBrush = new SolidBrush(textColor)) {
                drawing.DrawString(currencyCode, font, textBrush, 0, 0);
                drawing.Save();
            }
        }
        return retImg;
    }

回答by Andrew Taylor

Here is Panayiotis' version of Kazar's answer with optional parameters and documentation, suitable for adding to a library class.

这是 Panayiotis 版本的 Kazar 答案，带有可选参数和文档，适合添加到库类中。

/// <summary>
/// Creates an image containing the given text.
/// NOTE: the image should be disposed after use.
/// </summary>
/// <param name="text">Text to draw</param>
/// <param name="fontOptional">Font to use, defaults to Control.DefaultFont</param>
/// <param name="textColorOptional">Text color, defaults to Black</param>
/// <param name="backColorOptional">Background color, defaults to white</param>
/// <param name="minSizeOptional">Minimum image size, defaults the size required to display the text</param>
/// <returns>The image containing the text, which should be disposed after use</returns>
public static Image DrawText(string text, Font fontOptional=null, Color? textColorOptional=null, Color? backColorOptional=null, Size? minSizeOptional=null)
{
    Font font = Control.DefaultFont;
    if (fontOptional != null)
        font = fontOptional;

    Color textColor = Color.Black;
    if (textColorOptional != null)
        textColor = (Color)textColorOptional;

    Color backColor = Color.White;
    if (backColorOptional != null)
        backColor = (Color)backColorOptional;

    Size minSize = Size.Empty;
    if (minSizeOptional != null)
        minSize = (Size)minSizeOptional;

    //first, create a dummy bitmap just to get a graphics object
    SizeF textSize;
    using (Image img = new Bitmap(1, 1))
    {
        using (Graphics drawing = Graphics.FromImage(img))
        {
            //measure the string to see how big the image needs to be
            textSize = drawing.MeasureString(text, font);
            if (!minSize.IsEmpty)
            {
                textSize.Width = textSize.Width > minSize.Width ? textSize.Width : minSize.Width;
                textSize.Height = textSize.Height > minSize.Height ? textSize.Height : minSize.Height;
            }
        }
    }

    //create a new image of the right size
    Image retImg = new Bitmap((int)textSize.Width, (int)textSize.Height);
    using (var drawing = Graphics.FromImage(retImg))
    {
        //paint the background
        drawing.Clear(backColor);

        //create a brush for the text
        using (Brush textBrush = new SolidBrush(textColor))
        {
            drawing.DrawString(text, font, textBrush, 0, 0);
            drawing.Save();
        }
    }
    return retImg;
}