How to detect a PNG image is light or dark [closed] - php

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I am stuck in finding a solution for detecting the main brightness of a PNG image is light or dark. The concept is add a background for all PNG images but if it is too light then add a dark background
I have found some solutions by searching but seems they are working not well with the transparent background image. Could you gimme some ideas?
Some images and the expected result:
Expected result is dark:
https://www.dropbox.com/s/uzrda3133vvbp66/black_2.png?dl=0

Answer 1

it's interesting.
could you try this? and tell is this fit for you?
// Load the image using ImageMagick
$image = new \Imagick('path/to/image.png');
// Get the image dimensions
$width = $image->getImageWidth();
$height = $image->getImageHeight();
// Create a new Imagick object with a white background of the same size as the image
$background = new \Imagick();
$background->newImage($width, $height, 'white', 'png');
// Add the image to the background
$background->compositeImage($image, \Imagick::COMPOSITE_OVER, 0, 0);
// Convert the image to grayscale
$background->modulateImage(100, 0, 100);
// Get the histogram of the image
$histogram = $background->getImageHistogram();
// Count the number of pixels at each intensity level
$count = array_fill(0, 256, 0);
foreach ($histogram as $pixel) {
$color = $pixel->getColor();
$intensity = round(($color['r'] + $color['g'] + $color['b']) / 3);
$count[$intensity] += $pixel->getColorCount();
}
// Calculate the total number of pixels
$totalPixels = $width * $height;
// Calculate the total number of dark pixels (intensity < 128)
$darkPixels = array_sum(array_slice($count, 0, 128));
// Calculate the total number of light pixels (intensity >= 128)
$lightPixels = array_sum(array_slice($count, 128));
// Determine if the image is light or dark
$isLight = ($lightPixels / $totalPixels) > 0.5;
// Output the result
if ($isLight) {
echo 'The image is light';
} else {
echo 'The image is dark';
}
Note that this approach may not work well with images that have a lot of transparent areas, as those areas may skew the histogram towards one end or the other. In those cases, you may need to come up with a more sophisticated algorithm that takes into account the transparency of each pixel.

Answer 2

1 - Load the PNG image using ImageMagick and retrieve its color histogram. The color histogram will give us the distribution of colors in the image.
$image = new \Imagick('path/to/image.png');
$histogram = $image->getImageHistogram();
2 - Calculate the total number of pixels in the image. This will be used to calculate the average brightness of the image.
$total_pixels = $image->getImageWidth() * $image->getImageHeight();
3 - Loop through the color histogram and calculate the sum of the brightness values for each color.
$sum_brightness = 0;
foreach ($histogram as $pixel) {
$color = $pixel->getColor();
$brightness = ($color['r'] + $color['g'] + $color['b']) / 3;
$sum_brightness += $brightness * $pixel->getColorCount();
}
4 - Calculate the average brightness of the image by dividing the sum of the brightness values by the total number of pixels.
$average_brightness = $sum_brightness / $total_pixels;
5 - Determine whether the image is light or dark based on the average brightness. You can use a threshold value to determine whether the image is light or dark. For example, if the average brightness is less than 128 (out of 255), the image is considered dark. If the average brightness is greater than or equal to 128, the image is considered light.
if ($average_brightness < 128) {
// Image is dark
} else {
// Image is light
}
You can adjust the threshold value to suit your needs, depending on how you want to classify light and dark images.
Note that this algorithm assumes that the PNG image has a transparent background. If the image has a non-transparent background, you may need to modify the algorithm to account for the background color.