PHP crop blank space around image

gistfile1.php

<?php

/** Loop through all the files in a folder **/

function loop_through_folder_by_extension($path, $extension) {

	$processedFiles = array();
	$errors = array();

	foreach ( "{$path}/*.{$extension}" as $filename ) {

		// Process image

		// Save to destination

		// if there's an error you can save it to $errors[]
		// you can keep track of processed files in  $processedFiles[]

	} // end of loop

	// Output $errors and $processedFiles at the end if desired

} 





/**
 * Convert a PDF to a PNG using imagick class
 *
 * @param $filename PDF filename
 * @uses  imagick PHP class for ImageMagick
 */

function web32_pdf_to_png( $filename = null ) {
	
	$filename = 'pdf.pdf';
	
	if (!class_exists('imagick')) {
		echo "imagick PHP class not detected.";
		exit();
	}
	
	// $im = new imagick( $filename[0] );
	$im = new imagick( $filename );
	$im->setImageFormat( "png" );
	$im->getNumberImages(); // get number of pages (you can then loop through)
	$im->setResolution( 800, 800 ); //

	// If you're loading the PDF from a blob this is how you get the first page instead of the last page:
	// $im->readimageblob($blob);
	// $im->setiteratorindex(0);

	header( "Content-Type: image/png" );
	echo $im;

}


/**
 * Crops an image based on the color of the top left pixel
 * Works with images that have blank space around the image
 * Tested on PNGs with white and transparent backgrounds
 *
 * @param $img Image resource or filename
 * @uses ImageMagick
 */

function web32_cropwhitespacefromimage( $img = null ) {
	
	// If there's no image
	if (!$img) {
		echo 'no file';
		exit();
	}

	// If the $img is a filename, convert it into an image resource
	if (is_string($img)) {
		$img = imagecreatefrompng( $img );
	}


	// Get the width and height
	$width = imagesx($img);
	$height = imagesy($img);

	// Find the size of the borders
	$top = 0;
	$bottom = 0;
	$left = 0;
	$right = 0;

	$bgcolor = 0xFFFFFF; // Use this if you only want to crop out white space
	$bgcolor = imagecolorat( $img, $top, $left ); // This works with any color, including transparent backgrounds

	//top
	for(; $top < $height; ++$top) {
	  for($x = 0; $x < $width; ++$x) {
	    if(imagecolorat($img, $x, $top) != $bgcolor) {
	       break 2; //out of the 'top' loop
	    }
	  }
	}

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

	//left
	for(; $left < $width; ++$left) {
	  for($y = 0; $y < $height; ++$y) {
	    if(imagecolorat($img, $left, $y) != $bgcolor) {
	       break 2; //out of the 'left' loop
	    }
	  }
	}

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


	//copy the contents, excluding the border
	$newimg = imagecreate(
	    $width-($left+$right), $height-($top+$bottom));

	imagecopy($newimg, $img, 0, 0, $left, $top, imagesx($newimg), imagesy($newimg));

	//finally, output the image
	header("Content-Type: image/png");
	imagepng($newimg);
	
	
} // end of function





// web32_pdf_to_png('pdf.pdf');
web32_cropwhitespacefromimage('transparentbg.png');
// web32_cropwhitespacefromimage('chart2.png');

how to converted it i cant do it

can you show it with a example?? specially white bg crop

In the function file use
ob_start();
	 imagepng($newimg);
	 $imagedata = ob_get_contents();
	 return $imagedata;
---------------------------------
in function calling use

ob_start();
	web32_cropwhitespacefromimage($img);
	$cropped = ob_get_clean();