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In this tutorial article, we will discuss about resizing images in PHP.

Load the image before resizing

Before we can resize an image, we must first load it as an image resource in our script. This is file_get_contents()different from using a function like to get the contents of an image file. To load a file, we need to use functions like imagecreatefromjpeg(), imagecreatefrompng()and imagecreatefromgif(). Depending on the type of image we'll be resizing, we'll use different functions accordingly.

PHPgetimagesize()

After loading the image, we use getimagesize()to calculate the width, height, and type of the input image. This function returns a list of items where the width and height of the image are stored at index 0 and 1 respectively, and IMAGETYPE_XXXthe constant is stored at index 2. We will use the value of this constant returned to find out what type of image to use and what function to use.

<?php
function load_image($filename, $type) {
    $new = 'new34.jpeg';
    if( $type == IMAGETYPE_JPEG ) {
        $image = imagecreatefromjpeg($filename);
        echo "here is jpeg output:";
        imagejpeg($image, $new);

    }
    elseif( $type == IMAGETYPE_PNG ) {
        $image = imagecreatefrompng($filename);
        echo "here is png output:";
        imagepng($image,$new);
    }
    elseif( $type == IMAGETYPE_GIF ) {
        $image = imagecreatefromgif($filename);
        echo "here is gif output:";
        imagejpeg($image, $new);
    }
    return $new;
}

$filename = "panda.jpeg";
list($width, $height,$type) = getimagesize($filename);
echo "Width:" , $width,"\n";
echo "Height:", $height,"\n";
echo "Type:", $type, "\n";

$old_image = load_image($filename, $type);
?>

Input image:

Output:

Width:225
Height:225
Type:2
here is jpeg output:

Output image:

Both are the same image because we only load the image and calculate the size of the original image in this section.

PHPimagecopyresized()

imagecopyresized()Gets a rectangular area of ​​width and height from (src_x,src_y)at position and places it at position . It is an inbuilt function in PHP.src_imagesrc_wsrc_h(dst_x,dst_y) 处的目标图像的矩形区域中

<?php
// File and new size
$filename = 'panda.jpeg';
$percent = 0.5;

// Content type
header('Content-Type: image/jpeg');

// Get new sizes
list($width, $height, $type) = getimagesize($filename);
$newwidth = $width * $percent;
$newheight = $height * $percent;
$type = $list[2];
echo $type;
// Load
$thumb = imagecreatetruecolor($newwidth, $newheight);
$source = imagecreatefromjpeg($filename);

// Resize
imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);

// Output
imagejpeg($thumb,'new.jpeg');
?>

Input image:

Output image:

As mentioned above, imagecopyresize()the function accepts ten parameters, which are listed below.

It returns a Boolean value of TRUE on success and FALSE on failure.

PHPimagecopyresampled()

imagecopyresampled()Copies a rectangular portion of one image to another with different, seamlessly interpolated pixel values ​​to reduce the image size while maintaining a high degree of clarity.

It functions similarly imagecopyresized()to the resize function, with the added benefit of upsampling the image in addition to resizing it.

<?php
// The file
$filename = 'panda.jpeg';
$percent = 2;

// Content type
header('Content-Type: image/jpeg');

// Get new dimensions
list($width, $height) = getimagesize($filename);
$new_width = $width * $percent;
$new_height = $height * $percent;

// Resample
$image_p = imagecreatetruecolor($new_width, $new_height);
$image = imagecreatefromjpeg($filename);
imagecopyresampled($image_p, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);

// Output
imagejpeg($image_p, 'resampled1.jpeg', 100);
?>

Input image:

Output image:

The function imagecopyresampled()accepts ten different parameters.

PHPimagescale()

You specify the size instead of defining the width or height of the latest image. If you want the new image to be half the size of the first image, set the size to 0.8. Here is sample code that scales an image by a given factor while preserving its proportions.

We scale image()multiply the original width and height of the image by the ratio specified in the function.

Here is an example of it:

<?php
    
function load_image($filename, $type) {

        if( $type == IMAGETYPE_JPEG ) {
            $image = imagecreatefromjpeg($filename);

        }
        elseif( $type == IMAGETYPE_PNG ) {
            $image = imagecreatefrompng($filename);
           
        }
        elseif( $type == IMAGETYPE_GIF ) {
            $image = imagecreatefromgif($filename);
            
        }
        
        return $image;
    }
function scale_image($scale, $image, $width, $height) {
    $new_width = $width * $scale;
    $new_height = $height * $scale;
    return resize_image($new_width, $new_height, $image, $width, $height);
    
}
function resize_image($new_width, $new_height, $image, $width, $height) {
    $image12 = 'hello.jpeg';
    $new_imag = imagecreatetruecolor($new_width, $new_height);
    imagecopyresampled($new_imag, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
    
    return imagejpeg($new_imag, $image12);
    }


$filename = "panda.jpeg";
list($width, $height, $type) = getimagesize($filename);
$old_image = load_image($filename, $type);
$image_scaled = scale_image(0.8, $old_image, $width, $height);
?>

Input image:

Output image:

Apart from this, PHP has a built-in function that allows you to scale images to a specified width and height.

See the sample code.

<?php
    
$out_image = "sca.jpeg";
$image_name ="panda.jpeg";
     
// Load image file
$image = imagecreatefromjpeg($image_name);
  
// Use imagescale() function to scale the image
$img = imagescale( $image, 500, 400 );
  

header("Content-type: image/jpeg");
imagejpeg($img,$out_image);
  
?>

Input image:

Output_Image: