PHP Load image into array, 2 bit

Question

I want to load an entire image (PNG) into a 2-dimensional array where a black pixel is true and a white pixel is false.

What's the most efficient way of doing this?

Should I convert the image into bitmap and attempt to read that in, or is there a more efficient method?

Note: A black&white bitmap is 1-bit, because you only need 1 bit of information (black or white) for each pixel. — diracdeltafunk
– diracdeltafunk, Commented Jun 3, 2014 at 16:26

CodeCaster · Accepted Answer · 2011-11-23 10:45:26Z

4

This should do:

$image = imagecreatefrompng("input.png");
$width = imagesx($image);
$height = imagesy($image);
$colors = array();

for ($y = 0; $y < $height; $y++)
{
    for ($x = 0; $x < $width; $x++)
    {
        $rgb = imagecolorat($image, $x, $y);
        $r = ($rgb >> 16) & 0xFF;
        $g = ($rgb >> 8) & 0xFF;
        $b = $rgb & 0xFF;

        $black = ($r == 0 && $g == 0 && $b == 0);
        $colors[$x][$y] = $black;
    } 
}

A probably more efficient way would be using Imagick::exportImagePixels().

edited Nov 23, 2011 at 10:45

answered Nov 23, 2011 at 10:32

CodeCaster

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5 Comments

Alasdair Over a year ago

I know about imagecolorat(), and I'm looking for something more efficient. But thank you for your answer.

CodeCaster Over a year ago

@Alasdair you didn't mention that in your question. If you have ImageMagick, you can take a look at exportImagePixels() and loop through that array.

Alasdair Over a year ago

Sorry, I should have explained in more detail. The whole reason I want to do this is to bypass GD.

zaf Over a year ago

@Alasdair how much of GD do you want to bypass? You want to decode PNG in pure PHP? You want an offline task outside PHP?

Alasdair Over a year ago

I was planning to convert the PNG to bitmap and read this into an array, completely bypassing GD. But I've given up now. This answer here is technically correct, and I didn't phrase my question very well, so I will accept.

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