4 Steps To Add Watermark To Image In PHP – Simple Examples

By / Tips & Tutorials - PHP / November 26, 2021

Welcome to a tutorial on how to add a watermark to an image in PHP. So you have an eCommerce website or gallery that accepts image uploads, but there is just one problem. Some thieves are stealing the images, and a little bit of protection will do good.

We can use the GD extension in PHP to add a watermark to images:

  1. Open the original image – $img = imagecreatefromjpeg("IMAGE.JPG");
  2. Set the text color – $red = imagecolorallocatealpha($img, 255, 0, 0);
  3. Add the text to the image – imagettftext($img, 18, 0, 0, 24, $red, "PATH\FONT.TTF", "COPYRIGHT");
  4. Save the watermarked image – imagejpeg($img, "WATERMARKED.JPG", 60);

That covers the quick basics, but how do we apply another image as the watermark? Read one for more examples!

ⓘ I have included a zip file with all the example source code at the start of this tutorial, so you don’t have to copy-paste everything… Or if you just want to dive straight in.

 

 

QUICK SLIDES

How To Add Watermark To Image In PHP

 

TABLE OF CONTENTS

Download & Notes PHP Watermark Useful Bits & Links
Tutorial Video The End

 

DOWNLOAD & NOTES

First, here is the download link to the example source code as promised.

 

QUICK NOTES

  • Make sure that the GD extension is enabled in php.ini – extension=gd (or gd2 prior to PHP8).
  • For l-text.php and 3-text-pos.php, make sure $font = "PATH/TO/FONT" is correct and PHP has read access to the font file.
If you spot a bug, feel free to comment below. I try to answer short questions too, but it is one person versus the entire world… If you need answers urgently, please check out my list of websites to get help with programming.

 

EXAMPLE CODE DOWNLOAD

Click here to download the source code, I have released it under the MIT license, so feel free to build on top of it or use it in your own project.

 

 

ADDING WATERMARK WITH PHP

All right, let us now get into the examples of applying a watermark to an image in PHP now.

 

EXAMPLE 1) ADD TEXT WATERMARK TO IMAGE

1-text.php
<?php
// (X) QUICK FUNCTION REFERENCE
// imagecolorallocatealpha (IMAGE, RED, GREEN, BLUE, OPACITY)
// imagettftext(IMAGE, SIZE, ANGLE, X, Y, COLOR, FONT, TEXT)
// imagejpeg (IMAGE, FILE, QUALITY)

// (A) SETTINGS
$source = "doge.jpg"; // SOURCE IMAGE
$target = "watermarked.jpg"; // WATERMARKED IMAGE
$quality = 60; // WATERMARKED IMAGE QUALITY (0 to 100)
$copytxt = "Copyright"; // COPYRIGHT TEXT
$font = "C:\Windows\Fonts\arial.ttf"; // MAKE SURE PATH IS CORRECT!
$fontsize = 18; // FONT SIZE
$posX = 0; // PLACE WATERMARK AT LEFT OF IMAGE
$posY = 24; // PLACE WATERMARK AT TOP OF IMAGE

// (B) CREATE IMAGE OBJECT
$img = imagecreatefromjpeg($source);

// (C) WRITE TEXT TO IMAGE (TOP LEFT CORNER)
$fontcolor = imagecolorallocatealpha($img, 255, 0, 0, 75);
imagettftext($img, $fontsize, 0, $posX, $posY, $fontcolor, $font, $copytxt);

// (D) SAVE TO FILE
imagejpeg($img, $target, $quality);
echo "Saved to $target";

Look no further, this is pretty much the same steps as the above introduction snippet.

  1. A couple of settings – The source image file, watermark text, font to use, etc…
  2. Read the original image.
  3. Watermark the image.
  4. Save the watermarked image to a file.

 

 

EXAMPLE 2) ADD AN IMAGE WATERMARK

2-image.php
<?php
// (X) QUICK FUNCTION REFERENCE
/* imagecopy (
* DESTINATION, SOURCE,
* DESTINATION-X, DESTINATION-Y,
* SOURCE-X, SOURCE-Y,
* SOURCE-WITDTH, SOURCE-HEIGHT
* )
*/
 
// (A) SETTINGS
$sourceS = "doge.jpg"; // SOURCE IMAGE
$sourceW = "potato.png"; // WATERMARK IMAGE
$target = "watermarked.jpg"; // WATERMARKED IMAGE
$quality = 60; // WATERMARKED IMAGE QUALITY (0 to 100)
$posX = 0; // PLACE WATERMARK AT LEFT CORNER
$posY = 0; // PLACE WATERMARK AT TOP CORNER

// (B) CREATE IMAGE OBJECTS
$imgS = imagecreatefromjpeg($sourceS);
$imgW = imagecreatefrompng($sourceW);

// (C) APPLY WATERMARK
imagecopy(
  $imgS, $imgW, // COPY WATERMARK ONTO SOURCE IMAGE
  $posX, $posY, // PLACE WATERMARK AT TOP LEFT CORNER
  0, 0, imagesx($imgW), imagesY($imgW) // COPY FULL WATERMARK IMAGE WITHOUT CLIPPING
);

// (D) OUTPUT
imagejpeg($imgS, $target, $quality);
echo "Saved to $target";

This version will apply an image watermark instead, it is a lot more straightforward – We are just “copying” the watermark onto the uploaded image using imagecopy(). For the uninitiated, please use PNG WEBP GIF for the watermark image. JPEG does not support alpha channels (transparency).

 

 

EXAMPLE 3) POSITION (CENTER) THE TEXT WATERMARK

3-text-pos.php
<?php
// (A) SETTINGS
$source = "doge.jpg"; // SOURCE IMAGE
$target = "watermarked.jpg"; // WATERMARKED IMAGE
$quality = 60; // WATERMARKED IMAGE QUALITY (0 to 100)
$copytxt = "Copyright"; // COPYRIGHT TEXT
$font = "C:\Windows\Fonts\arial.ttf"; // MAKE SURE PATH IS CORRECT!
$fontsize = 18; // FONT SIZE

// (B) CREATE IMAGE OBJECT
$img = imagecreatefromjpeg($source);

// (C) POSITION CALCULATIONS
// (C1) SOURCE IMAGE DIMENSIONS
$widthS = imagesx($img);
$heightS = imagesy($img);

// (C2) TEXT BOX DIMENSIONS
$sizeT = imagettfbbox($fontsize, 0, $font, $copytxt);
$widthT = max([$sizeT[2], $sizeT[4]]) - min([$sizeT[0], $sizeT[6]]);
$heightT = max([$sizeT[5], $sizeT[7]]) - min([$sizeT[1], $sizeT[3]]);

// (C3) CENTER POSITION
$posX = CEIL(($widthS - $widthT) / 2);
$posY = CEIL(($heightS - $heightT) / 2);
if ($posX < 0 || $posY < 0) { exit("Text is too long"); } // OPTIONAL ERROR HANDLE

// (D) WRITE TEXT TO IMAGE
$fontcolor = imagecolorallocatealpha($img, 255, 0, 0, 30);
imagettftext($img, $fontsize, 0, $posX, $posY, $fontcolor, $font, $copytxt);

// (E) SAVE TO FILE
imagejpeg($img, $target, $quality);
echo "Saved to $target";

This is the same as above, but with additional calculations to center the text watermark… How positioning works is unfortunately very Mathematical. Not going to explain line-by-line, but in a summary:

  • Use imagesx() and imagesy() to get the dimensions of the source image.
  • Use $sizeT = imagettfbbox() to get an array of 8 numbers, which are the X-Y coordinates of the text box (illustration below).

  • To calculate the dimensions of the text box:
    • For the width, take the rightmost point max([$sizeT[2], $sizeT[4]]), minus the leftmost point min([$sizeT[0], $sizeT[6]]).
    • For the height, take the topmost point max([$sizeT[5], $sizeT[7]]), minus the bottommost point min([$sizeT[1], $sizeT[3]]).
  • With that, we can finally do calculations to center the text.
    • Horizontal center = (Image Width - Text Width) / 2.
    • Vertical center = (Image Height - Text Height) / 2.

 

 

EXAMPLE 4) POSITION (CENTER) THE IMAGE WATERMARK

4-image-pos.php
<?php
// (A) SETTINGS
$sourceS = "doge.jpg"; // SOURCE IMAGE
$sourceW = "potato.png"; // WATERMARK IMAGE
$target = "watermarked.jpg"; // WATERMARKED IMAGE
$quality = 60; // WATERMARKED IMAGE QUALITY (0 to 100)

// (B) CREATE IMAGE OBJECTS
$imgS = imagecreatefromjpeg($sourceS);
$imgW = imagecreatefrompng($sourceW);

// (C) POSITION CALCULATIONS
// (C1) SOURCE & WATERMARK DIMENSIONS
$widthS = imagesx($imgS);
$heightS = imagesY($imgS);
$widthW = imagesx($imgW);
$heightW = imagesY($imgW);

// (C2) CENTER POSITION
$posX = CEIL(($widthS - $widthW) / 2);
$posY = CEIL(($heightS - $heightW) / 2);
if ($posX < 0 || $posY < 0) { exit("Watermark image is too large"); } // OPTIONAL ERROR HANDLE

// (D) APPLY WATERMARK
imagecopy(
  $imgS, $imgW, // COPY WATERMARK ONTO SOURCE IMAGE
  $posX, $posY, // PLACE WATERMARK AT TOP LEFT CORNER
  0, 0, $widthW, $heightW // COPY FULL WATERMARK IMAGE WITHOUT CLIPPING
);

// (E) OUTPUT
imagejpeg($imgS, $target, $quality);
echo "Saved to $target";

Finally, centering an image watermark is also… Mathematical. But it is thankfully a lot simpler:

  • Horizontal Center = (Source Width - Watermark Width) / 2
  • Vertical Center = (Source Height - Watermark Height) / 2

 

 

USEFUL BITS & LINKS

That’s all for this guide, and here is a small section on some extras and links that may be useful to you.

 

HOW TO SET THE OPACITY OF THE IMAGE WATERMARK?

Unfortunately, the GD library doesn’t seem to have a straightforward method to set image opacity. So, use your own image editor to set the watermark opacity.

 

SUMMARY – USEFUL GD FUNCTIONS

Function Description Reference Link
imagecreatefromjpeg() Create a GD image object from a JPG file. Click Here
imagecolorallocatealpha() Allocates a color with alpha (transparency). Click Here
imagettftext() Writes text to the image using TTF. Click Here
imagesx() Get the width of an image. Click Here
imagesy() Get the height of an image. Click Here
imagettfbbox() Get the dimensions of a block of text. Click Here
imagecopy() Copy an image onto another image. Click Here
imagejpeg() Save to a JPEG image file. Click Here

 

LINKS & REFERENCES

 

TUTORIAL VIDEO

 

INFOGRAPHIC CHEAT SHEET

How To Add Watermark In PHP (Click to Enlarge)

 

THE END

Thank you for reading, and we have come to the end of this guide. I hope that it has helped you with your project, and if you want to share anything with this guide, please feel free to comment below. Good luck and happy coding!

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