imagecropauto

In some cases the use of the IMG_CROP_WHITE or IMG_CROP_BLACK does not work. The function returns FALSE. It is best to use the IMG_CROP_THRESHOLD mode and specify the color in fourth argument as in the example below :<?php$original_img = imagecreatefromjpeg($image_path);// Use this :$cropped_img_white = imagecropauto($original_img , IMG_CROP_THRESHOLD, null, 16777215);// Rather than :$cropped_img_white = imagecropauto($original_img , IMG_CROP_WHITE);// AND// Use this :$cropped_img_black = imagecropauto($original_img , IMG_CROP_THRESHOLD, null, 0);// Rather than :$cropped_img_black = imagecropauto($original_img , IMG_CROP_BLACK);?>

I don’t know why you can’t set the threshold for the four sides filter (IMG_CROP_SIDES) so here’s how to do it manually using the IMG_CROP_THRESHOLD filter instead.$threshold = .5;$im = imagecreatefromjpeg('somefile.jpg');$width = imagesx($im);$height = imagesy($im);$arr = [    [0,0],    [$width-1,0],    [0,$height-1],    [$width-1,$height-1],];$red = 0;$green = 0;$blue = 0;// grab the colours from all four cornersforeach( $arr as $arr2 ) {    $thisColor = imagecolorat($im, $arr2[0], $arr2[1]);     $rgb = imagecolorsforindex($im, $thisColor);     $red += round(round(($rgb['red'] / 0x33)) * 0x33);     $green += round(round(($rgb['green'] / 0x33)) * 0x33);     $blue += round(round(($rgb['blue'] / 0x33)) * 0x33); }// and average them$red /= 4;$green /= 4;$blue /= 4;$newColor = imagecolorallocate($im, $red, $green, $blue);            $cropped = imagecropauto($im, IMG_CROP_THRESHOLD, $threshold, $newColor);imagejpg($cropped, 'somefile.cropped.jpg');imagedestroy($im);imagedestroy($cropped);