PHP development thumbnail operation file

Operation file

<?php
/*打开图片*/
$src = "https://img.php.cn/upload/course/000/000/004/581454f755fb1195.jpg";
$info = getimagesize($src);
$type = image_type_to_extension($info[2],false);
$fun = "imagecreatefrom{$type}";
$image = $fun($src);
/*操作图片*/
//在内存中建立一个宽300高200的真色彩图片
$image_thumb = imagecreatetruecolor(300,200);
//将原图复制到新建的真色彩图片上，并且按照一定比例压缩(参数1：真色彩图片,参数2：原图，参数3,4,5,6：原图和真色彩图的起始点，参数7,8：原图和真色彩图的结束点，参数9：原图宽，参数10：原图高)
imagecopyresampled($image_thumb,$image,0,0,0,0,300,200,$info[0],$info[1]);
//销毁原始图片
imagedestroy($image);
?>

Code explanation:

First create a color canvas of specified size in the memory.

imagecreatetruecolor() Returns an image identifier, representing an image of size Black image of x_size and y_size.

Using the function imagecopyresampled()

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

imagecopyresampled() copies a square area in one image to another image, inserting pixel values ​​smoothly, Thus, inter alia, the size of the image is reduced while still maintaining great sharpness.

dst_image

Target image connection resource.

src_image

Source image connection resource.

dst_x

Target X coordinate point.

dst_y

Target Y coordinate point.

src_x

The X coordinate point of the source.

src_y

The Y coordinate point of the source.

dst_w

Target width.

dst_h

Target height.

src_w

The width of the source image.

src_h

The height of the source image.

Then destroy the picture copied in the memory.