5 more advanced GD examples to manipulate images with PHP

#php #beginners #programming #webdev

1. How to draw pie chart

<?php

$data = [50, 90, 150, 360];

$im = imagecreatetruecolor(400, 300);
$c_black = imageColorAllocate($im, 0,0,0);

foreach ( $data as $i => $v ) {
  $c = imageColorAllocate(
    $im, 46 + $i * 30,204 - $i * 30, 64 + $i * 30
  );
  imagefilledarc(
    $im, 200, 150,
    100 + $i * 10, 100 + $i * 10, $i ? $data[$i-1] : 0,
    $v, $c, IMG_ARC_PIE
  );
}

imagePng($im, '/tmp/image.png');

$data - sample data to draw pie chart based on,
imagecreatetruecolor - creates true color GD image object with specified width & height,
imageColorAllocate - creates color object to use for pie (we use $i value to randomize color),
imagefilledarc - draw next pie,
200, 150 - pie center coordinates,
imagePng - saves image in PNG format to the given path.

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2. How to flip an image

<?php

$file = '/var/www/examples/heroine.png';
$im = imagecreatefrompng($file);

imageflip( $im, IMG_FLIP_VERTICAL );
imagePng($im, '/tmp/image.png');

$file - image to rotate,
imagecreatefrompng - creates GD image object from given PNG image,
imageflip - flips given image in a specified direction,
IMG_FLIP_VERTICAL - flips image vertically, explore other options,
imagePng - saves image in PNG format to the given path.

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3. How to get pixel color

$file = '/var/www/examples/heroine.png';
$im = imagecreatefrompng($file);
$c = imagecolorat($im, 100, 100);
list($r, $g, $b) = [($c >> 16) & 0xFF, ($c >> 8) & 0xFF, $c & 0xFF];

$file - sample image to work with,
imagecreatefrompng - creates GD image object from given PNG image,
imagecolorat - returns color at a given position as an integer,
100, 100 - we're getting color on 100 pixels from top and 100 pixels from left,
$r, $g, $b - variables will contain decoded values for R, G and B color channels.

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4. How to rotate an image

<?php

$file = '/var/www/examples/heroine.png';
$im = imagecreatefrompng($file);

$c_black = imageColorAllocate($im, 0,0,0);
$imr = imagerotate( $im, 90, $c_black );

imagePng($imr, '/tmp/image.png');

$file - image to rotate,
imagecreatefrompng - creates GD image object from given PNG image,
imageColorAllocate - creates color object to later use in image,
imagerotate - rotates given image and returns new gd image object,
90 - rotate image by 90 degrees,
$c_black - color to use for background (if necessary),
imagePng - saves image in PNG format to the given path.

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5. How to set line thickness

<?php

$im = imagecreatetruecolor(400, 300);

$c_black = imageColorAllocate($im, 0,0,0);
$c_green = imageColorAllocate($im, 46,204,64);

for ( $thick = 5; $thick > 0; $thick-- ) {
  imageline($im, 50, 50 + $thick, 350, 250 + $thick, $c_green);
}


imagePng($im, '/tmp/image.png');

imagecreatetruecolor - creates true color GD image object with specified width & height,
imageColorAllocate - creates color object to later use in image,
imageline - draws line using given coordinates and color,
$thick = 5 - resulting line thickness (5 in our case),
imagePng - saves image in PNG format to the given path.

Open original or edit on Github.