Crop whitespace from image in PHP

Is it possible to remove the whitespace surrounding an image in PHP?

NOTE: to clarify I mean something like photoshops trim feature.

Thanks.

To trim all whitespace, as you call it, surrounding the interesting part of the image, first we find out where the "whitespace" stops, and then we copy everything inside of those borders.

//load the image
$img = imagecreatefromjpeg("http://ecx.images-amazon.com/images/I/413XvF0yukL._SL500_AA280_.jpg");

//find the size of the borders
$b_top = 0;
$b_btm = 0;
$b_lft = 0;
$b_rt = 0;

//top
for(; $b_top < imagesy($img); ++$b_top) {
  for($x = 0; $x < imagesx($img); ++$x) {
    if(imagecolorat($img, $x, $b_top) != 0xFFFFFF) {
       break 2; //out of the 'top' loop
    }
  }
}

//bottom
for(; $b_btm < imagesy($img); ++$b_btm) {
  for($x = 0; $x < imagesx($img); ++$x) {
    if(imagecolorat($img, $x, imagesy($img) - $b_btm-1) != 0xFFFFFF) {
       break 2; //out of the 'bottom' loop
    }
  }
}

//left
for(; $b_lft < imagesx($img); ++$b_lft) {
  for($y = 0; $y < imagesy($img); ++$y) {
    if(imagecolorat($img, $b_lft, $y) != 0xFFFFFF) {
       break 2; //out of the 'left' loop
    }
  }
}

//right
for(; $b_rt < imagesx($img); ++$b_rt) {
  for($y = 0; $y < imagesy($img); ++$y) {
    if(imagecolorat($img, imagesx($img) - $b_rt-1, $y) != 0xFFFFFF) {
       break 2; //out of the 'right' loop
    }
  }
}

//copy the contents, excluding the border
$newimg = imagecreatetruecolor(
    imagesx($img)-($b_lft+$b_rt), imagesy($img)-($b_top+$b_btm));

imagecopy($newimg, $img, 0, 0, $b_lft, $b_top, imagesx($newimg), imagesy($newimg));

//finally, output the image
header("Content-Type: image/jpeg");
imagejpeg($newimg);

My old example, that assumes an identical "border" on all sides of the image, just to clarify the comments :)

//load the image
$img = imagecreatefromjpeg("img.jpg");

//find the size of the border.
$border = 0;
while(imagecolorat($img, $border, $border) == 0xFFFFFF) {
  $border++;
}

//copy the contents, excluding the border
//This code assumes that the border is the same size on all sides of the image.
$newimg = imagecreatetruecolor(imagesx($img)-($border*2), imagesy($img)-($border*2));
imagecopy($newimg, $img, 0, 0, $border, $border, imagesx($newimg), imagesy($newimg));

//finally, if you want, overwrite the original image
imagejpeg($newimg, "img.jpg");

Gnud's script redundantly calls imagesx and imagesy. It also iterates every pixel on every side, even when the corners overlap. This improved version eliminates redundant function calls and checks every pixel only once, granting a significant increase in speed. The function returns a status ($result['#']) equal to 2 if every pixel is the trimmed.

example();
function example(){
    $img = imagecreatefromjpeg("http://ecx.images-amazon.com/images/I/413XvF0yukL._SL500_AA280_.jpg");

    // find the trimmed image border
    $box = imageTrimBox($img);

    // copy cropped portion
    $img2 = imagecreate($box['w'], $box['h']);
    imagecopy($img2, $img, 0, 0, $box['l'], $box['t'], $box['w'], $box['h']);

    // output cropped image to the browser
    header('Content-Type: image/png');
    imagepng($img2);

    imagedestroy($img);
    imagedestroy($img2);
}



function imageTrimBox($img, $hex=null){
if (!ctype_xdigit($hex)) $hex = imagecolorat($img, 0,0);
$b_top = $b_lft = 0;
$b_rt = $w1 = $w2 = imagesx($img);
$b_btm = $h1 = $h2 = imagesy($img);

do {
    //top
    for(; $b_top < $h1; ++$b_top) {
        for($x = 0; $x < $w1; ++$x) {
            if(imagecolorat($img, $x, $b_top) != $hex) {
                break 2;
            }
        }
    }

    // stop if all pixels are trimmed
    if ($b_top == $b_btm) {
        $b_top = 0;
        $code = 2;
        break 1;
    }

    // bottom
    for(; $b_btm >= 0; --$b_btm) {
        for($x = 0; $x < $w1; ++$x) {
            if(imagecolorat($img, $x, $b_btm-1) != $hex) {
                break 2;
            }
        }
    }

    // left
    for(; $b_lft < $w1; ++$b_lft) {
        for($y = $b_top; $y <= $b_btm; ++$y) {
            if(imagecolorat($img, $b_lft, $y) != $hex) {
                break 2;
            }
        }
    }

    // right
    for(; $b_rt >= 0; --$b_rt) {
        for($y = $b_top; $y <= $b_btm; ++$y) {
            if(imagecolorat($img, $b_rt-1, $y) != $hex) {
                break 2;
            }
        }

    }

    $w2 = $b_rt - $b_lft;
    $h2 = $b_btm - $b_top;
    $code = ($w2 < $w1 || $h2 < $h1) ? 1 : 0;
} while (0);

// result codes:
// 0 = Trim Zero Pixels
// 1 = Trim Some Pixels
// 2 = Trim All Pixels
return array(
    '#'     => $code,   // result code
    'l'     => $b_lft,  // left
    't'     => $b_top,  // top
    'r'     => $b_rt,   // right
    'b'     => $b_btm,  // bottom
    'w'     => $w2,     // new width
    'h'     => $h2,     // new height
    'w1'    => $w1,     // original width
    'h1'    => $h1,     // original height
);
}

I know this is pretty old but if you have ImageMagick enabled you can use this method

Trim Image

PHP's gd library has the imagecropauto function (PHP version 5.5+):

<?php 
$img=imagecreatefrompng("tux.png"); // Load and instantiate the image
if($img) {
  $cropped=imagecropauto($img,IMG_CROP_DEFAULT); // Auto-crop the image

  imagedestroy($img); // Clean up as $img is no longer needed

  header("Content-type: image/png"); // Set the appropriate header so the browser
                                     // knows how to present it
  imagepng($cropped); // Return the newly cropped image
}

By default imagecropauto will try to crop using transparency, and then fall back on using the 4 corners of the image to attempt to detect the background to crop; I have also had success with the following constants in place of IMG_CROP_AUTO in the example above:

IMG_CROP_BLACK - Useful for images with a black background
IMG_CROP_WHITE - Useful for images with a white background
IMG_CROP_THRESHOLD - Allows you to set a colour and threshold to use when cropping

Crop whitespace from image in PHP

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