With PHP / GD, how do I crop an image?

Question

I want to simulate the behavior of cropping Photoshop (crop an area covered by the same color on all sides) using GD and PHP , but I lack an idea on how to do this.

If someone knows how to do this, I would really like to hear it.

Thanks in advance.

Answer 1

The easiest solution I can think of is:

• Find out the color of the top left pixel.
• , , , , . , , . , x y imagecopy *().

, .

BTW, ImageMagick : http://www.imagemagick.org/Usage/crop/#trim

Answer 2

( ):

// Trims an image then optionally adds padding around it.
// $im  = Image link resource
// $bg  = The background color to trim from the image
// $pad = Amount of padding to add to the trimmed image
//        (acts simlar to the "padding" CSS property: "top [right [bottom [left]]]")
function imagetrim(&$im, $bg, $pad=null){

    // Calculate padding for each side.
    if (isset($pad)){
        $pp = explode(' ', $pad);
        if (isset($pp[3])){
            $p = array((int) $pp[0], (int) $pp[1], (int) $pp[2], (int) $pp[3]);
        }else if (isset($pp[2])){
            $p = array((int) $pp[0], (int) $pp[1], (int) $pp[2], (int) $pp[1]);
        }else if (isset($pp[1])){
            $p = array((int) $pp[0], (int) $pp[1], (int) $pp[0], (int) $pp[1]);
        }else{
            $p = array_fill(0, 4, (int) $pp[0]);
        }
    }else{
        $p = array_fill(0, 4, 0);
    }

    // Get the image width and height.
    $imw = imagesx($im);
    $imh = imagesy($im);

    // Set the X variables.
    $xmin = $imw;
    $xmax = 0;

    // Start scanning for the edges.
    for ($iy=0; $iy<$imh; $iy++){
        $first = true;
        for ($ix=0; $ix<$imw; $ix++){
            $ndx = imagecolorat($im, $ix, $iy);
            if ($ndx != $bg){
                if ($xmin > $ix){ $xmin = $ix; }
                if ($xmax < $ix){ $xmax = $ix; }
                if (!isset($ymin)){ $ymin = $iy; }
                $ymax = $iy;
                if ($first){ $ix = $xmax; $first = false; }
            }
        }
    }

    // The new width and height of the image. (not including padding)
    $imw = 1+$xmax-$xmin; // Image width in pixels
    $imh = 1+$ymax-$ymin; // Image height in pixels

    // Make another image to place the trimmed version in.
    $im2 = imagecreatetruecolor($imw+$p[1]+$p[3], $imh+$p[0]+$p[2]);

    // Make the background of the new image the same as the background of the old one.
    $bg2 = imagecolorallocate($im2, ($bg >> 16) & 0xFF, ($bg >> 8) & 0xFF, $bg & 0xFF);
    imagefill($im2, 0, 0, $bg2);

    // Copy it over to the new image.
    imagecopy($im2, $im, $p[3], $p[0], $xmin, $ymin, $imw, $imh);

    // To finish up, we replace the old image which is referenced.
    $im = $im2;
}