Resize Images in PHP (With 3 Lines Of Code!)

Welcome to a tutorial on how to resize images in PHP. So you have a project that deals with images, and want to resize them due to space restrictions… or maybe you just want to create thumbnails of the uploaded images.

That covers the basics, but let us walk through with a few detailed examples – Read on!

 

 

TABLE OF CONTENTS

 

 

EXAMPLE CODE DOWNLOAD

Source code on GitHub Gist

Just click on “download zip” or do a git clone. I have released it under the MIT license, so feel free to build on top of it or use it in your own project.

 

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TUTORIAL VIDEO

 

1) SIMPLE IMAGE RESIZE

<?php
// (A) READ THE ORIGINAL IMAGE
$original = imagecreatefrompng("resize.png"); // original 400 x 600 px

// (B) RESIZE IMAGE
// IMG_NEAREST_NEIGHBOUR, IMG_BILINEAR_FIXED, IMG_BICUBIC, IMG_BICUBIC_FIXED
$resized = imagescale($original, 200, 300, IMG_BICUBIC); // 50% smaller

// (C) SAVE RESIZED IMAGE
imagewebp($resized, "demoA.webp", 70);

// (D) OPTIONAL - CLEAN UP
imagedestroy($original);
imagedestroy($resized);

As in the introduction snippet, the process is as easy as opening, resizing, and saving. But to add on:

1. Take note that we use different imagecreatefromABC functions to open different image formats.
2. imagescale takes in 4 parameters.
   • The first is the original image.
   • Followed by the width and height.
   • Lastly, an optional resize mode. IMG_BICUBIC will produce “smoother edges”, and IMG_NEAREST_NEIGHBOUR gives “sharp edges”.
3. Finally, we also use the respective imageXYZ functions to save to different image formats.
4. Optional, clean up the image objects from the memory.

 

 

2) RESIZE IMAGE FUNCTION

<?php
function resizer ($source, $destination, $size, $quality=null) {
// $source - Original image file
// $destination - Resized image file name
// $size - Single number for percentage resize
// Array of 2 numbers for fixed width + height
// $quality - Optional image quality. JPG & WEBP = 0 to 100, PNG = -1 to 9
 
  // (A) CHECKS
  if (!file_exists($source)) { throw new Exception("Source image file not found"); }
  $sExt = strtolower(pathinfo($source)["extension"]);
  $dExt = strtolower(pathinfo($destination)["extension"]);
  $allowed = ["bmp", "gif", "jpg", "jpeg", "png", "webp"];
  if (!in_array($sExt, $allowed)) { throw new Exception("$sExt - Invalid image file type"); }
  if (!in_array($dExt, $allowed)) { throw new Exception("$dExt - Invalid image file type"); }
  if ($quality != null) {
    if (in_array($dExt, ["jpg", "jpeg", "webp"]) && ($quality<0 || $quality>100)) { $quality = 70; }
    if ($dExt == "png" && ($quality<-1 || $quality>9)) { $quality = -1; }
    if (!in_array($dExt, ["png", "jpg", "jpeg", "webp"])) { $quality = null; }
  }

  // (B) NEW IMAGE DIMENSIONS
  if (is_array($size)) {
    $new_width = $size[0];
    $new_height = $size[1];
  } else {
    $dimensions = getimagesize($source);
    $new_width = ceil(($size/100) * $dimensions[0]);
    $new_height = ceil(($size/100) * $dimensions[1]);
  }

  // (C) RESIZE
  $fnCreate = "imagecreatefrom" . ($sExt=="jpg" ? "jpeg" : $sExt);
  $original = $fnCreate($source);
  $resized = imagescale($original, $new_width, $new_height, IMG_BICUBIC);

  // (D) OUTPUT & CLEAN UP
  $fnOutput = "image" . ($dExt=="jpg" ? "jpeg" : $dExt);
  if (is_numeric($quality)) {
    $fnOutput($resized, $destination, $quality);
  } else {
    $fnOutput($resized, $destination);
  }
  imagedestroy($original);
  imagedestroy($resized);
}

// (E) EXAMPLE USAGE
// (E1) PERCENTAGE RESIZE
resizer("resize.png", "demoB.jpg", 50);
resizer("resize.png", "demoC.png", 25);

// (E2) FIXED DIMENSION RESIZE + QUALITY
resizer("resize.png", "demoD.png", [100, 150], -1);
resizer("resize.png", "demoE.webp", [200, 300], 60);

It is a real hassle to manually change imagecreatefromABC and imageXYZ, so I have packaged a function to help you guys.

• To resize by percentage – resizer(ORIGINAL, DESTINATION, PERCENTAGE)
• To resize to an exact dimension – resizer(ORIGINAL, DESTINATION, [WIDTH, HEIGHT])
• Lastly, you can also specify the image quality.
  • For JPG, JPEG, WEBP – resizer(ORIGINAL, DESTINATION, DIMENSION, 0 TO 100)
  • For PNG – resizer(ORIGINAL, DESTINATION, DIMENSION, -1 TO 9)

 

 

3) EXTRACT PART OF IMAGE & RESIZE

<?php
// (A) READ THE ORIGINAL IMAGE
$original = imagecreatefrompng("resize.png");

// (B) EMPTY CANVAS WITH REQUIRED DIMENSIONS
$resized = imagecreatetruecolor(150, 150);

// (C) EXTRACT PART OF ORIGINAL IMAGE ONTO EMPTY CANVAS
imagecopyresampled(
  $resized, $original, // to resized, from original
  0, 0, 100, 200, // dest-x, dest-y, src-x, src-y
  150, 150, 200, 200 // dest-w, dest-h, src-w, src-h
);

// (E) SAVE/OUTPUT RESIZED IMAGE
imagewebp($resized, "demoF.webp", 70);

// (F) OPTIONAL - CLEAN UP
imagedestroy($original);
imagedestroy($resized);

Finally, we can also extract and resize a part of the image. Slightly more roundabout:

1. imagecreatefrompng() – Load the source image as usual.
2. imagecreatetruecolor() – Create an empty canvas.
3. imagecopyresampled() – “Copy” part of the source image onto the empty canvas.
4. imagewebp() – Save it.

 

 

 

SUMMARY OF FUNCTIONS

Function	Description	PHP Manual
imagecreatefromjpeg(FILE)	The whole family of imagecreatefromABC() functions are used to create an image object from the specified file.	Click Here
imagescale(SOURCE, WIDTH, HEIGHT, MODE)	Resize the image.	Click Here
imagecreatetruecolor(WIDTH, HEIGHT)	Create an empty canvas with the specified width and height.	Click Here
imagecopyresampled(DESTINATION, SOURCE, DX, DY, SX, SY)	Copy part of the source image and resize.	Click Here
imagejpeg(IMAGE, FILE NAME)	The whole family of imageXYZ() is used to save and output an image object.	Click Here
imagedestroy(IMAGE)	Destroy an image.	Click Here

 

LINKS & REFERENCES

• How do I resize pngs with transparency in PHP? – StackOverflow
• PHP Image Resize – PHPPot