Detailed explanation of PHP image generation function

PHP image generation function is a very powerful functional module in the PHP language, which can be used to dynamically generate images, thus providing developers with great room for creativity. The more commonly used image generation functions include imagecreate(), imagecreatetruecolor(), etc.

This article will explain the PHP image generation function in detail to provide readers with a more detailed understanding.

1. imagecreate() function

imagecreate() is the most basic and common image generation function in PHP. This function accepts two parameters, which are the width and height of the generated image. The usage is as follows:

$width = 100;
$height = 50;

$image = imagecreate($width, $height);

The above code will create a blank image with a width of 100 pixels and a height of 50 pixels. This image can Used for subsequent drawing operations.

2. imagecreatetruecolor() function

imagecreatetruecolor() function can create a true color image. Compared with the image generated by the imagecreate() function, it has better color performance and is more Delicate gradient and shadow effects.

$width = 100;
$height = 50;

$image = imagecreatetruecolor($width, $height);

The above code will create a true color blank image with a width of 100 pixels and a height of 50 pixels.

3. Drawing operation

After generating a blank image, we can then use the drawing functions provided by PHP to perform drawing operations. The more common drawing functions include:

1. imagefill(): Color used to fill the image.

$bg_color = imagecolorallocate($image, 255, 255, 255);
imagefill($image, 0, 0, $bg_color);

The above code will fill the entire background of the $image image with white.

2. imagesetpixel(): Draw a pixel on the image.

$pixel_color = imagecolorallocate($image, 0, 0, 0);
imagesetpixel($image, 10, 10, $pixel_color);

The above code will draw a black pixel on the $image image with coordinates (10, 10).

3. imageline(): Draw a straight line on the image.

$line_color = imagecolorallocate($image, 0, 0, 0);
imageline($image, 0, 0, 100, 50, $line_color);

The above code will draw a black straight line from (0,0) to (100,50) on the $image image.

4. imagestring(): Draw a string on the image.

$text_color = imagecolorallocate($image, 0, 0, 0);
imagestring($image, 5, 0, 0, "Hello World!", $text_color);

The above code will draw a black "Hello World!" string on the $image image.

4. Image output

After the above drawing operation, we can output the generated image. The more common output methods include:

1. header () function and imagepng() function

header("Content-type:image/png");
imagepng($image);
imagedestroy($image);

The above code will output the generated image in png format.

2. imagejpeg() function

header("Content-type:image/jpeg");
imagejpeg($image);
imagedestroy($image);

The above code will output the generated image in jpeg format.

3. imagewbmp() function

header("Content-type:image/vnd.wap.wbmp");
imagewbmp($image);
imagedestroy($image);

The above code will output the generated image in wbmp format.

5. Summary

PHP image generation function integrates various common functions of image processing, making operations such as thumbnail processing, verification code generation, and watermark addition more convenient. This article introduces the basic usage of PHP image generation functions and common drawing operations. I hope it can be of some help to readers.

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