Bitmap/Histogram: Difference between revisions

=={{header|PHP}}==

<lang PHP>

define('src_name', 'input.jpg'); // source image

define('dest_name', 'output.jpg'); // destination image

$img = imagecreatefromjpeg(src_name); // read image

if(empty($img)){

echo 'Image could not be loaded!';

exit;

}

$black = imagecolorallocate($img, 0, 0, 0);

$white = imagecolorallocate($img, 255, 255, 255);

$width = imagesx($img);

$height = imagesy($img);

$array_lum = array(); // for storage of luminosity of each pixel

$sum_lum = 0; // total sum of luminosity

$average_lum = 0; // average luminosity of whole image

for($x = 0; $x < $width; $x++){

for($y = 0; $y < $height; $y++){

// read pixel value

$color = imagecolorat($img, $x, $y);

$r = ($color >> 16) & 0xFF;

$g = ($color >> 8) & 0xFF;

$b = $color & 0xFF;

// save pixel luminosity in temporary array

$array_lum[$x][$y] = ($r + $g + $b);

// add pixel luminosity to sum

$sum_lum += $array_lum[$x][$y];

}

}

// calculate average luminosity

$average_lum = $sum_lum / ($width * $height);

for($x = 0; $x < $width; $x++){

for($y = 0; $y < $height; $y++){

// pixel is brighter than average -> set white

// else -> set black

if($array_lum[$x][$y] > $average_lum){

imagesetpixel($img, $x, $y, $white);

}

else{

imagesetpixel($img, $x, $y, $black);

}

}

}

// save black and white image to dest_name

imagejpeg($img, dest_name);

if(!file_exists(dest_name)){

echo 'Image not saved! Check permission!';

}

</lang>