调整图像大小而不扭曲比例（JPEGGIF或PNG）

Posted 2021-02-24

A function that resizes an image to desired width and height, but does not distort the image proportions. Works for JPEG, GIF and PNG.

<?php
/**
 * This function resizes an image to $fitInWidth and $fitInHeight, but doesn't distort the image proportions
 * 
 * $path: The full path to the image. Ex.: "/images/my_image.jpg"
 * 
 * $newName: If you don't want to override the original image, you can specify a new name.
 * 
 * $fitInWidth:The height in pixels that you want to fit the image in
 * 
 * $fitInHeight: The height in pixels that you want to fit the image in
 * 
 * $jpegQuality: If the image is a jpeg, the function will save 
 * the resized jpeg with the specified quality from 1 to 100
 */
function resize_image($path, $fitInWidth, $fitInHeight, $newName = '', $jpegQuality = 100)
{
	list($width, $height, $type) = getimagesize($path);//Getting image information
 
	$scaleW = $fitInWidth/$width;
	$scaleH = $fitInHeight/$height;
	if($scaleH > $scaleW)
	{
		$new_width = $fitInWidth;
		$new_height = floor($height * $scaleW);
	}
	else
	{
		$new_height = $fitInHeight;			
		$new_width = floor($width * $scaleH);
	}
	$new_path = $newName == '' ? $path : dirname($path) . '/' . $newName;
 
	if($type == IMAGETYPE_JPEG)//If image is jpeg
	{
		$image_now = imagecreatefromjpeg($path);//Get image from path
		$image_new = imagecreatetruecolor($new_width, $new_height);//Create new image from scratch
		//Copy image from path into new image ($image_new) with new sizes
		imagecopyresampled($image_new, $image_now, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
		imagejpeg($image_new, $new_path, $jpegQuality);
	}
	else if($type == IMAGETYPE_GIF)//If image is gif
	{
		$image_now = imagecreatefromgif($path);
		$image_new = imagecreatetruecolor($new_width, $new_height);
		imagecopyresampled($image_new, $image_now, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
		imagegif($image_new, $new_path);
	}
	else if($type == IMAGETYPE_PNG)//If image is png
	{
	    $image_now = imagecreatefrompng($path);
	    $image_new = imagecreatetruecolor($new_width, $new_height);
	    //Setting black color as transparent because image is png
	    imagecolortransparent($image_new, imagecolorallocate($image_new, 0, 0, 0));
		imagecopyresampled($image_new, $image_now, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
	    imagepng($image_new, $new_path);
	}
	else
	{
		//Image type is not jpeg, gif or png.
	}
	imagedestroy($image_now);
	imagedestroy($image_new);
}
 
//How to use
$img_path = 'images/my_image.jpg';//The path to the image you want to resize
//Here i'm giving a new name to the resized image so that it doesn't override the original  image. If you want to override the original image change: $new_name = '';
$new_name = 'resized_image.jpg';
resize_image($img_path, 200, 200, $new_name);
?>