PHP Image graphics operation of the basic use of the GD library tutorial

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1>GD Library Introduction

GD refers to the graphic device,php of the GD library is used to process graphics extension library, through the GD Library provides a series of APIs, you can process the image or directly generate new images.
In addition to the text processing, PHP, through the GD library, JPG, PNG, GIF, SWF and other images can be processed. GD library is commonly used in image watermarking, verification code generation and so on.
PHP is already integrated with the GD library by default and only needs to be opened when it is installed.

General process for creating images

1. Set the header to tell the browser which MIME type you want to generate
   

2. Create an image area that will be based on this image area in future operations
   

3. Draw a fill background in a blank image area
   

4. Draw a graphic outline on the background enter text
   

5. Output Final graphic
   

6. Clear All Resources
   

7. Other page calls
   

Header ("Content-type:image/png"); $img =imagecreatetruecolor (+), $red =imagecolorallocate ($img, 0xFF, 0x00, 0x00); Imagefill ($img, 0, 0, $red); Imagepng ($img); Imagedestroy ($img);

1. Draw lines
   Imageline ()
   Syntax: Imageline (

   Sx

   EX,

   COL);
   

2. Draw a Circle
   Imagearc ()
   Syntax: Imagearc (

   CX,

   W

   StartAngle,

   color)

$img = Imagecreatetruecolor (200, 200);//Assign Color $red = imagecolorallocate ($img, 255, 0, 0); $white = Imagecolorallocate ($img, 255, 255, 255);//background filled with white Imagefill ($img, 0,0, $white);//Draw a red round imagearc ($img, N, N,,, 0, $red); Imagepng ($i MG);//Release Memory Imagedestroy ($IMG);

1. Draw a rectangle
   Imagerectangle ()
   Syntax: Imagerectangle (

   X1,

   X2,

   Col

$img = Imagecreatetruecolor (200, 200);//Assign Color $red = imagecolorallocate ($img, 255, 0, 0); $white = Imagecolorallocate ($img, 255, 255, 255); Imagefill ($img, 0,0, $white);//Draw a red rectangle Imagerectangle ($img, 50,50,100, $red); Imagepng ($img);// Free memory Imagedestroy ($IMG);

1. Draw text
   Grammar 1:imagestring (

   Font,

   Y

   COL)
   Grammar 2:imagettftext (

   Size

   X

   Color

   Text

Header ("Content-type:image/png");//imagestring font size cannot be set $img = Imagecreatetruecolor (+); $red = Imagecolorallocate ($img, 0xFF, 0x00, 0x00); Imagestring ($img, 5, ten, "Hello World", $red); Imagepng ($img); Imagedestroy ($img), $img 1=imagecreatetruecolor (200,200), $red =imagecolorallocate ($img 1,255,0,0); $white Imagecolorallocate ($img 1,255,255,255); Imagefill ($img 1,0,0, $red); $font = "C:\Windows\Fonts\simhei.ttf"; Imagettftext ($img 1,23,0,100,100, $white, $font, "How are You"); Imagepng ($img 1); Imagedestroy ($img 1);

1. Draw a noise point
   Syntax: Imagesetpixel (

   X

   Col

Draw 10 noise for ($i =0; $i <10; $i + +) {  imagesetpixel ($img, rand (0), rand (0,), $black);   Imagesetpixel ($img, rand (0, +), rand (0, +), $green);}

Output image file
through Imagepng you can directly output an image to a browser, save the image to a file by specifying a path parameter
1. Imagepng ()
Meaning: Save picture in PNG format
Syntax: imag Epng (

filename)
2. imagejpeg ()
Meaning: Save picture to JPEG format
Syntax: imagepng (filename, $quality)
3. Imagegif ()
Meaning: Save a picture in GIF format
Syntax: imagegif (filename)

Case:
1. Randomly generated verification code (PHP)
2. Add a watermark to a picture