(Advanced article) PHP Image processing Technology-GD Library

1. Open GD Extension

Extension=php_gd2.dll

Apache restart

2. Example:

Scene:

Make a green picture of 500x300

① Creating a canvas

Canvas, a resource-based data. An image resource that can be manipulated.

Create a new canvas (new)

Imagecreate (wide, high) creates a palette-based canvas.

Imagecreatetruecolor (wide, high); Create a true color canvas.

Create a canvas based on a picture (open)

Imagecreatefromjpeg (image address);

Imagecreatefrompng (image address);

Imagecreatefromgif (image address);

② manipulating the canvas

Assign color: If you need to use a color on the canvas, you should first assign the color to the canvas.

Using functions:

Color identification = imagecolorallocate (canvas, r,g,b);

How colors are represented:

Rgb

③ Fill canvas: Fills (replaces) fill points, contiguous and identical points of color

Using functions:

Imagefill (canvas, fill position x, fill position y, color identification) complete

Location is managed using coordinates:

Origin: 0, 0, the upper-left corner of the canvas.

To the right, the X axis increases and the downward Y axis increases.

Lower right corner coordinates: width-1,height-1

④ Output Canvas

Output the drawing information that is processed in the canvas.

Typical of:

1 output to picture file.

2 Direct output.

Using functions:

Imagepng (canvas [, File address]):

Imagejpeg ();

Imagegif ();

If there is no second argument, the direct output is indicated.

Note: If you print directly to the browser, you need to tell the browser that the type of response data should be a picture in PNG format:

Use instruction Content-type;

One canvas can be output multiple times, output to various formats

⑤ Destroying Canvas Resources

Imagedestroy ()

Example code:

<?php//For example: Make 500x300 green picture $width=500; $height =300;//Create a true Color canvas $img=imagecreatetruecolor ($width, $height);//Var_ Dump ($img);    Test Result: Resource (2) of type (GD)   $img is a resource type//Use function imagecolorallocate (canvas, r,g,b) to assign color, color representation: R  G  b$green =imagecolorallocate ($img, 0x0, 0xFF, 0x0);//Fill Canvas, Origin: 0, 0, upper left corner of canvas, Imagefill (canvas, fill position x, fill position y, color identification) complete Imagefill ($img, 0,0 , $green);//output canvas, direct output to the current path as a picture file, in the format of PNG, JPEG, Gif//imagepng ($img, './green.png ');  If there is no second parameter, the direct output//If the direct output to the browser, you need to tell the browser, the type of response data should be a picture in PNG format: Use instruction Content-typeheader (' content-type:image/png; '); Imagepng ($img);//NOTE: A canvas can be output multiple times, output for various formats//Destroy Canvas resources Imagedestroy ($IMG);

Example code:

<?php//For example: Make 500x300 green picture $width=500; $height =300;//Create a true Color canvas $img=imagecreatetruecolor ($width, $height);//Var_ Dump ($img);    Test Result: Resource (2) of type (GD)   $img is a resource type//Use function imagecolorallocate (canvas, r,g,b) to assign color, color representation: R  G  b$green =imagecolorallocate ($img, 0x0, 0xFF, 0x0);//Fill Canvas, Origin: 0, 0, upper left corner of canvas, Imagefill (canvas, fill position x, fill position y, color identification) complete Imagefill ($img, 0,0 , $green);//output canvas, direct output to the current path as a picture file, in the format of PNG, JPEG, Gif//imagepng ($img, './green.png ');  If there is no second parameter, the direct output//If the direct output to the browser, you need to tell the browser, the type of response data should be a picture in PNG format: Use instruction Content-typeheader (' content-type:image/png; '); Imagepng ($img);//NOTE: A canvas can be output multiple times, output for various formats//Destroy Canvas resources Imagedestroy ($IMG);

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