PHP image processing functions: image processing technology of imagecreatefrompng, imagecopyresampled, imagettftext and other functions

PHP is a high-level programming language that is widely used in web application development. In web applications, image processing is a very common requirement. In PHP, there are many built-in image processing functions, such as imagecreatefrompng, imagecopyresampled, imagettftext, etc. These functions can be used to crop, zoom, watermark, add text, etc. to images. This article details these functions, how to use them, and provides specific code examples.

1. Imagecreatefrompng function

The imagecreatefrompng function is used to create a new image resource from a PNG image file. Its syntax is as follows:

resource imagecreatefrompng ( string $filename )

Among them, $filename means to open The path to the PNG file.

The following is a sample code for image resources created by the imagecreatefrompng function:

//指定PNG文件
$filename = "image.png";

//打开PNG文件并创建图像资源
$image = imagecreatefrompng($filename);

//输出图像
header('Content-Type: image/png');
imagepng($image);

//销毁图像资源
imagedestroy($image);

2. Imagecopyresampled function

The imagecopyresampled function is used to perform operations such as cropping, scaling, and rotating images. The syntax is as follows:

bool imagecopyresampled ( $dst_image , $src_image ,
                          $dst_x , $dst_y ,
                          $src_x , $src_y ,
                          $dst_w , $dst_h ,
                          $src_w , $src_h )

Among them, $dst_image represents the target image resource, $src_image represents the source image resource, $dst_x and $dst_y represent the starting coordinates in the target image, $src_x and $src_y represent the source image The starting coordinates in , $dst_w and $dst_h represent the width and height of the target image, $src_w and $src_h represent the width and height of the source image.

The following is a sample code for the imagecopyresampled function to scale an image:

//指定JPG文件
$filename = "image.jpg";

//打开JPG文件并创建图像资源
$image = imagecreatefromjpeg($filename);

//缩放图像
$width = imagesx($image) / 2;
$height = imagesy($image) / 2;
$thumb_image = imagecreatetruecolor($width, $height);
imagecopyresampled($thumb_image, $image, 0, 0, 0, 0, $width, $height, imagesx($image), imagesy($image));

//输出图像
header('Content-Type: image/jpeg');
imagejpeg($thumb_image);

//销毁图像资源
imagedestroy($image);
imagedestroy($thumb_image);

3. Imagettftext function

The imagettftext function is used to add text to an image. Its syntax is as follows:

bool imagettftext ( $image , $size , $angle , $x , $y , $color ,
                    $fontfile , $text )

Among them, $image represents the image resource to add text, $size represents the font size, $angle represents the font tilt angle, $x and $y represent the starting coordinates of the text, $color represents the font color, $fontfile Represents the path of the font file, $text represents the text to be added.

The following is a sample code for adding text to an image using the imagettftext function:

//指定JPG文件
$filename = "image.jpg";

//打开JPG文件并创建图像资源
$image = imagecreatefromjpeg($filename);

//添加文字
$text = "Hello World!";
$font_size = 30;
$font_color = imagecolorallocate($image, 255, 255, 255);
$font_file = "arial.ttf";
imagettftext($image, $font_size, 0, 10, 50, $font_color, $font_file, $text);

//输出图像
header('Content-Type: image/jpeg');
imagejpeg($image);

//销毁图像资源
imagedestroy($image);

To sum up, PHP provides numerous image processing functions, and we can use them to meet various processing needs. This article introduces three commonly used functions: imagecreatefrompng, imagecopyresampled, imagettftext, and gives corresponding usage examples. By learning the use of these functions, we can process images more efficiently and conveniently.

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