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C # use gdi+ to add text to the picture and make the text adaptive to the rectangular area
2022-07-04 09:34:00 【Dandelion_ drq】
demand
The requirement is to make a page for editing text . Users write text on the web , The text area is a rectangular box , Users can adjust the text size by dragging the bar below .
Here's the picture :
When submitting data, the upper left corner and lower right corner of the front-end text area are positioned to the background . Because the font size unit of the front end has nothing to do with the back end , So you can't directly transfer the font size , That is, the back end should calculate the appropriate font size according to the rectangular area and text content .
Simply put, you know the rectangular area of the text , And the text , The text content should be adjusted to the appropriate font size according to the size of the rectangular area, which can fill this area appropriately .
analysis & Ideas
Graphics
Class has a MeasureString
Method , It can be used to calculate how many pixels the text written in the current font will occupy .
as follows :
//
// Abstract :
// Specified for measurement System.Drawing.Font Draw the specified string .
//
// Parameters :
// text:
// String to measure .
//
// font:
// System.Drawing.Font, It defines the text format of the string .
//
// Return results :
// This method returns System.Drawing.SizeF structure , The structure represents text Parameter specified 、 Use font Parameter to draw the size of the string , Unit by System.Drawing.Graphics.PageUnit
// Attribute specifies .
//
// abnormal :
// T:System.ArgumentException:
// font by null.
public SizeF MeasureString(string text, Font font);
This method returns SizeF
contain Width
and Height
attribute , Reading these two attributes can get the width and height of the text content ( In pixels ).
//
// Abstract :
// Get or set this System.Drawing.SizeF The horizontal component of the structure .
//
// Return results :
// this System.Drawing.SizeF The horizontal component of the structure , Usually measured in pixels .
public float Width { get; set; }
// Abstract :
// Get or set this System.Drawing.SizeF The vertical component of the structure .
//
// Return results :
// this System.Drawing.SizeF The vertical component of the structure , Usually measured in pixels .
public float Height { get; set; }
So we can first locate according to the upper left corner and lower right corner of the text transmitted from the front , Calculate the rectangular area of the text , Then estimate a font size , Reuse MeasureString
Method calculate the area occupied by the estimated text , Compare with the actual text area size , If it is large, the font will be reduced , If it is small, increase the font . In this way, you can roughly find the appropriate text size .
Concrete realization
- Add text method
/// <summary>
/// Add text to the picture , Text size adaptive
/// </summary>
/// <param name="imgPath"> Picture path </param>
/// <param name="locationLeftTop"> Top left positioning (x1,y1)</param>
/// <param name="locationRightBottom"> Position in the lower right corner (x2,y2)</param>
/// <param name="text"> Written content </param>
/// <param name="fontName"> Font name </param>
/// <returns> After adding text Bitmap object </returns>
public static Bitmap AddText(string imgPath, string locationLeftTop, string locationRightBottom, string text, string fontName = " Chinese Xingkai ")
{
Image img = Image.FromFile(imgPath);
int width = img.Width;
int height = img.Height;
Bitmap bmp = new Bitmap(width, height);
Graphics graph = Graphics.FromImage(bmp);
// Calculate the text area
// top left corner
string[] location = locationLeftTop.Split(',');
float x1 = float.Parse(location[0]);
float y1 = float.Parse(location[1]);
// The lower right corner
location = locationRightBottom.Split(',');
float x2 = float.Parse(location[0]);
float y2 = float.Parse(location[1]);
// Area width and height
float fontWidth = x2 - x1;
float fontHeight = y2 - y1;
float fontSize = fontHeight; // For the first time, the height of the text area is used as the size of the text font , Make adjustments later , Unit is px
Font font = new Font(fontName, fontSize, GraphicsUnit.Pixel);
SizeF sf = graph.MeasureString(text, font);
int times = 0;
// Adjust the font size to fit the text area
if (sf.Width > fontWidth)
{
while (sf.Width > fontWidth)
{
fontSize -= 0.1f;
font = new Font(fontName, fontSize, GraphicsUnit.Pixel);
sf = graph.MeasureString(text, font);
times++;
}
Console.WriteLine(" It was estimated to be big at first , The final font size is {0}, Circulated {1} Time ", font.ToString(), times);
}
else if (sf.Width < fontWidth)
{
while (sf.Width < fontWidth)
{
fontSize += 0.1f;
font = new Font(fontName, fontSize, GraphicsUnit.Pixel);
sf = graph.MeasureString(text, font);
times++;
}
Console.WriteLine(" It was estimated to be small at first , The final font size is {0}, Circulated {1} Time ", font.ToString(), times);
}
// The area occupied by the final font is generally not exactly equal to the actual area
// So according to the difference between the two areas, put the starting position of the text ( Top left positioning ) A little adjustment
x1 += (fontWidth - sf.Width) / 2;
y1 += (fontHeight - sf.Height) / 2;
graph.DrawImage(img, 0, 0, width, height);
graph.DrawString(text, font, new SolidBrush(Color.Black), x1, y1);
graph.Dispose();
img.Dispose();
return bmp;
}
- Test call
private static void Main(string[] args)
{
try
{
DrawingEntity drawing = new DrawingEntity();
Console.WriteLine("Start drawing ...");
System.Drawing.Bitmap bmp = drawing.AddText(@"D:\test\39585148.png", "177.75,63.84", "674.73, 141.6", " The sea , All waves ");
bmp.Save(@"D:\test\output.png");
bmp.Dispose();
Console.WriteLine("Done!");
}
catch (System.Exception ex)
{
Console.WriteLine(" Something went wrong !!\n" + ex.ToString());
}
finally
{
System.Console.WriteLine("\nPress any key to continue ...");
System.Console.ReadKey();
}
}
Final effect :
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