WordPress/wp-admin/includes/image.php

<?php

function get_udims( $width, $height) {
	if ( $height <= 96 && $width <= 128 )
		return array( $width, $height);
	elseif ( $width / $height > 4 / 3 )
		return array( 128, (int) ($height / $width * 128 ));
	else
		return array( (int) ($width / $height * 96 ), 96 );
}

function wp_create_thumbnail( $file, $max_side, $effect = '' ) {

		// 1 = GIF, 2 = JPEG, 3 = PNG

	if ( file_exists( $file ) ) {
		$type = getimagesize( $file );

		// if the associated function doesn't exist - then it's not
		// handle. duh. i hope.

		if (!function_exists( 'imagegif' ) && $type[2] == 1 ) {
			$error = __( 'Filetype not supported. Thumbnail not created.' );
		}
		elseif (!function_exists( 'imagejpeg' ) && $type[2] == 2 ) {
			$error = __( 'Filetype not supported. Thumbnail not created.' );
		}
		elseif (!function_exists( 'imagepng' ) && $type[2] == 3 ) {
			$error = __( 'Filetype not supported. Thumbnail not created.' );
		} else {

			// create the initial copy from the original file
			if ( $type[2] == 1 ) {
				$image = imagecreatefromgif( $file );
			}
			elseif ( $type[2] == 2 ) {
				$image = imagecreatefromjpeg( $file );
			}
			elseif ( $type[2] == 3 ) {
				$image = imagecreatefrompng( $file );
			}

			if ( function_exists( 'imageantialias' ))
				imageantialias( $image, TRUE );

			$image_attr = getimagesize( $file );

			// figure out the longest side

			if ( $image_attr[0] > $image_attr[1] ) {
				$image_width = $image_attr[0];
				$image_height = $image_attr[1];
				$image_new_width = $max_side;

				$image_ratio = $image_width / $image_new_width;
				$image_new_height = $image_height / $image_ratio;
				//width is > height
			} else {
				$image_width = $image_attr[0];
				$image_height = $image_attr[1];
				$image_new_height = $max_side;

				$image_ratio = $image_height / $image_new_height;
				$image_new_width = $image_width / $image_ratio;
				//height > width
			}

			$thumbnail = imagecreatetruecolor( $image_new_width, $image_new_height);
			@ imagecopyresampled( $thumbnail, $image, 0, 0, 0, 0, $image_new_width, $image_new_height, $image_attr[0], $image_attr[1] );

			// If no filters change the filename, we'll do a default transformation.
			if ( basename( $file ) == $thumb = apply_filters( 'thumbnail_filename', basename( $file ) ) )
				$thumb = preg_replace( '!(\.[^.]+)?$!', '.thumbnail' . '$1', basename( $file ), 1 );

			$thumbpath = str_replace( basename( $file ), $thumb, $file );

			// move the thumbnail to its final destination
			if ( $type[2] == 1 ) {
				if (!imagegif( $thumbnail, $thumbpath ) ) {
					$error = __( "Thumbnail path invalid" );
				}
			}
			elseif ( $type[2] == 2 ) {
				if (!imagejpeg( $thumbnail, $thumbpath ) ) {
					$error = __( "Thumbnail path invalid" );
				}
			}
			elseif ( $type[2] == 3 ) {
				if (!imagepng( $thumbnail, $thumbpath ) ) {
					$error = __( "Thumbnail path invalid" );
				}
			}

		}
	} else {
		$error = __( 'File not found' );
	}

	if (!empty ( $error ) ) {
		return $error;
	} else {
		return apply_filters( 'wp_create_thumbnail', $thumbpath );
	}
}

function wp_crop_image( $src_file, $src_x, $src_y, $src_w, $src_h, $dst_w, $dst_h, $src_abs = false, $dst_file = false ) {
	if ( ctype_digit( $src_file ) ) // Handle int as attachment ID
		$src_file = get_attached_file( $src_file );

	$src = wp_load_image( $src_file );

	if ( !is_resource( $src ))
		return $src;

	$dst = imagecreatetruecolor( $dst_w, $dst_h );

	if ( $src_abs ) {
		$src_w -= $src_x;
		$src_h -= $src_y;
	}

	if (function_exists('imageantialias'))
		imageantialias( $dst, true );

	imagecopyresampled( $dst, $src, 0, 0, $src_x, $src_y, $dst_w, $dst_h, $src_w, $src_h );

	if ( !$dst_file )
		$dst_file = str_replace( basename( $src_file ), 'cropped-'.basename( $src_file ), $src_file );

	$dst_file = preg_replace( '/\\.[^\\.]+$/', '.jpg', $dst_file );

	if ( imagejpeg( $dst, $dst_file ) )
		return $dst_file;
	else
		return false;
}

function wp_generate_attachment_metadata( $attachment_id, $file ) {
	$attachment = get_post( $attachment_id );

	$metadata = array();
	if ( preg_match('!^image/!', get_post_mime_type( $attachment )) ) {
		$imagesize = getimagesize($file);
		$metadata['width'] = $imagesize['0'];
		$metadata['height'] = $imagesize['1'];
		list($uwidth, $uheight) = get_udims($metadata['width'], $metadata['height']);
		$metadata['hwstring_small'] = "height='$uheight' width='$uwidth'";
		$metadata['file'] = $file;

		$max = apply_filters( 'wp_thumbnail_creation_size_limit', 3 * 1024 * 1024, $attachment_id, $file );

		if ( $max < 0 || $metadata['width'] * $metadata['height'] < $max ) {
			$max_side = apply_filters( 'wp_thumbnail_max_side_length', 128, $attachment_id, $file );
			$thumb = wp_create_thumbnail( $file, $max_side );

			if ( @file_exists($thumb) )
				$metadata['thumb'] = basename($thumb);
		}
	}
	return apply_filters( 'wp_generate_attachment_metadata', $metadata );
}

function wp_load_image( $file ) {
	if ( ctype_digit( $file ) )
		$file = get_attached_file( $file );

	if ( !file_exists( $file ) )
		return sprintf(__("File '%s' doesn't exist?"), $file);

	if ( ! function_exists('imagecreatefromstring') )
		return __('The GD image library is not installed.');

	$contents = file_get_contents( $file );

	$image = imagecreatefromstring( $contents );

	if ( !is_resource( $image ) )
		return sprintf(__("File '%s' is not an image."), $file);

	return $image;
}

function wp_shrink_dimensions( $width, $height, $wmax = 128, $hmax = 96 ) {
	if ( $height <= $hmax && $width <= $wmax )
		return array( $width, $height);
	elseif ( $width / $height > $wmax / $hmax )
		return array( $wmax, (int) ($height / $width * $wmax ));
	else
		return array( (int) ($width / $height * $hmax ), $hmax );
}

?>