PHP绘制渐变颜色图片

原文在: http://planetozh.com/blog/my-projects/images-php-gd-gradient-fill/ 使用范例如下 ,基本函数封装在gd-gradient-fill.php中, require_once('/path/to/gd-gradient-fill.php'); $image = new gd_gradient_fill($width,$height,$direction,$startcol

原文在:

http://planetozh.com/blog/my-projects/images-php-gd-gradient-fill/

使用范例如下,基本函数封装在gd-gradient-fill.php中,

    require_once('/path/to/gd-gradient-fill.php');
    $image = new gd_gradient_fill($width,$height,$direction,$startcolor,$endcolor,$step); 

gd_gradient_fill有5个必要参数和一个可选参数:

1. integer $width
   Width of the image
2. integer $height
   Height of the image
3. string $direction
   The shape or direction of the gradient, which can be any of : vertical, horizontal, ellipse, ellipse2, circle, circle2, rectangle, diamond.
4. string $startcolor
   Gradient start color, 3 or 6 digit hexadecimal ("#ff0" or "#dd4578")
5. string $endcolor
   Gradient end color
6. Optional : $step
   Breaks the gradient smooth blending

下面是一些实例,颜色从#101040渐变到#a1a1ff, 渐变方向不同, 鼠标移动到图片上可看到提示信息.

另外, 这个函数处理非矩形图片一样可以.

附函数源码如下:

<?php /*
Script Name: GD Gradient Fill
Script URI: http://planetozh.com/blog/my-projects/images-php-gd-gradient-fill/
Description: Creates a gradient fill of any shape (rectangle, ellipse, vertical, horizontal, diamond)
Author: Ozh
Version: 1.1
Author URI: http://planetozh.com/
*/

/* Release history :
 * 1.1
 *		- changed : more nicely packaged as a class
 *		- fixed : not displaying proper gradient colors with image dimension greater than 255 (because of a limitation in imagecolorallocate)
 *		- added : optional parameter 'step', more options for 'direction'
 * 1.0
 *		- initial release
 */

/* Usage :
 *
 * require_once('/path/to/gd-gradient-fill.php');
 * $image = new gd_gradient_fill($width,$height,$direction,$startcolor,$endcolor,$step);
 *
 * Parameters :
 *		- width and height : integers, dimesions of your image.
 *		- direction : string, shape of the gradient.
 *		  Can be : vertical, horizontal, rectangle (or square), ellipse, ellipse2, circle, circle2, diamond.
 *		- startcolor : string, start color in 3 or 6 digits hexadecimal.
 *		- endcolor : string, end color in 3 or 6 digits hexadecimal.
 *		- step : integer, optional, default to 0. Step that breaks the smooth blending effect.
 * Returns a resource identifier.
 *
 * Examples :
 *
 * 1.
 * require_once('/home/ozh/www/includes/gd-gradient-fill.php');
 * $image = new gd_gradient_fill(200,200,'horizontal','#fff','#f00');
 *
 * 2.
 * require_once('c:/iis/inet/include/gd-gradient-fill.php');
 * $myimg = new gd_gradient_fill(80,20,'diamond','#ff0010','#303060');
 *
 */


// Test it :
// $image = new gd_gradient_fill(400,200,'ellipse','#f00','#000',0);

class gd_gradient_fill {
	
	// Constructor. Creates, fills and returns an image
	function gd_gradient_fill($w,$h,$d,$s,$e,$step=0) {
		$this->width = $w;
		$this->height = $h;
		$this->direction = $d;
		$this->startcolor = $s;
		$this->endcolor = $e;
		$this->step = intval(abs($step));

		// Attempt to create a blank image in true colors, or a new palette based image if this fails
		if (function_exists('imagecreatetruecolor')) {
			$this->image = imagecreatetruecolor($this->width,$this->height);
		} elseif (function_exists('imagecreate')) {
			$this->image = imagecreate($this->width,$this->height);
		} else {
			die('Unable to create an image');
		}
		
		// Fill it
		$this->fill($this->image,$this->direction,$this->startcolor,$this->endcolor);
		
		// Show it		
		$this->display($this->image);
		
		// Return it
		return $this->image;
	}
	
	
	// Displays the image with a portable function that works with any file type
	// depending on your server software configuration
	function display ($im) {
		if (function_exists("imagepng")) {
			header("Content-type: image/png");
			imagepng($im);
		}
		elseif (function_exists("imagegif")) {
			header("Content-type: image/gif");
			imagegif($im);
		}
		elseif (function_exists("imagejpeg")) {
			header("Content-type: image/jpeg");
			imagejpeg($im, "", 0.5);
		}
		elseif (function_exists("imagewbmp")) {
			header("Content-type: image/vnd.wap.wbmp");
			imagewbmp($im);
		} else {
			die("Doh ! No graphical functions on this server ?");
		}
		return true;
	}
	
	
	// The main function that draws the gradient
	function fill($im,$direction,$start,$end) {
		
		switch($direction) {
			case 'horizontal':
				$line_numbers = imagesx($im);
				$line_width = imagesy($im);
				list($r1,$g1,$b1) = $this->hex2rgb($start);
				list($r2,$g2,$b2) = $this->hex2rgb($end);
				break;
			case 'vertical':
				$line_numbers = imagesy($im);
				$line_width = imagesx($im);
				list($r1,$g1,$b1) = $this->hex2rgb($start);
				list($r2,$g2,$b2) = $this->hex2rgb($end);
				break;
			case 'ellipse':
				$width = imagesx($im);
				$height = imagesy($im);
				$rh=$height>$width?1:$width/$height;
				$rw=$width>$height?1:$height/$width;
				$line_numbers = min($width,$height);
				$center_x = $width/2;
				$center_y = $height/2;
				list($r1,$g1,$b1) = $this->hex2rgb($end);
				list($r2,$g2,$b2) = $this->hex2rgb($start);
				imagefill($im, 0, 0, imagecolorallocate( $im, $r1, $g1, $b1 ));
				break;
			case 'ellipse2':
				$width = imagesx($im);
				$height = imagesy($im);
				$rh=$height>$width?1:$width/$height;
				$rw=$width>$height?1:$height/$width;
				$line_numbers = sqrt(pow($width,2)+pow($height,2));
				$center_x = $width/2;
				$center_y = $height/2;
				list($r1,$g1,$b1) = $this->hex2rgb($end);
				list($r2,$g2,$b2) = $this->hex2rgb($start);
				break;
			case 'circle':
				$width = imagesx($im);
				$height = imagesy($im);
				$line_numbers = sqrt(pow($width,2)+pow($height,2));
				$center_x = $width/2;
				$center_y = $height/2;
				$rh = $rw = 1;
				list($r1,$g1,$b1) = $this->hex2rgb($end);
				list($r2,$g2,$b2) = $this->hex2rgb($start);
				break;
			case 'circle2':
				$width = imagesx($im);
				$height = imagesy($im);
				$line_numbers = min($width,$height);
				$center_x = $width/2;
				$center_y = $height/2;
				$rh = $rw = 1;
				list($r1,$g1,$b1) = $this->hex2rgb($end);
				list($r2,$g2,$b2) = $this->hex2rgb($start);
				imagefill($im, 0, 0, imagecolorallocate( $im, $r1, $g1, $b1 ));
				break;
			case 'square':
			case 'rectangle':
				$width = imagesx($im);
				$height = imagesy($im);
				$line_numbers = max($width,$height)/2;
				list($r1,$g1,$b1) = $this->hex2rgb($end);
				list($r2,$g2,$b2) = $this->hex2rgb($start);
				break;
			case 'diamond':
				list($r1,$g1,$b1) = $this->hex2rgb($end);
				list($r2,$g2,$b2) = $this->hex2rgb($start);
				$width = imagesx($im);
				$height = imagesy($im);
				$rh=$height>$width?1:$width/$height;
				$rw=$width>$height?1:$height/$width;
				$line_numbers = min($width,$height);
				break;
			default:
		}
		
		for ( $i = 0; $i step ) {
			// old values :
			$old_r=$r;
			$old_g=$g;
			$old_b=$b;
			// new values :
			$r = ( $r2 - $r1 != 0 ) ? intval( $r1 + ( $r2 - $r1 ) * ( $i / $line_numbers ) ): $r1;
			$g = ( $g2 - $g1 != 0 ) ? intval( $g1 + ( $g2 - $g1 ) * ( $i / $line_numbers ) ): $g1;
			$b = ( $b2 - $b1 != 0 ) ? intval( $b1 + ( $b2 - $b1 ) * ( $i / $line_numbers ) ): $b1;
			// if new values are really new ones, allocate a new color, otherwise reuse previous color.
			// There's a "feature" in imagecolorallocate that makes this function
			// always returns '-1' after 255 colors have been allocated in an image that was created with
			// imagecreate (everything works fine with imagecreatetruecolor)
			if ( "$old_r,$old_g,$old_b" != "$r,$g,$b") 
				$fill = imagecolorallocate( $im, $r, $g, $b );
			switch($direction) {
				case 'vertical':
					imagefilledrectangle($im, 0, $i, $line_width, $i+$this->step, $fill);
					break;
				case 'horizontal':
					imagefilledrectangle( $im, $i, 0, $i+$this->step, $line_width, $fill );
					break;
				case 'ellipse':
				case 'ellipse2':
				case 'circle':
				case 'circle2':
					imagefilledellipse ($im,$center_x, $center_y, ($line_numbers-$i)*$rh, ($line_numbers-$i)*$rw,$fill);
					break;
				case 'square':
				case 'rectangle':
					imagefilledrectangle ($im,$i*$width/$height,$i*$height/$width,$width-($i*$width/$height), $height-($i*$height/$width),$fill);
					break;
				case 'diamond':
					imagefilledpolygon($im, array (
						$width/2, $i*$rw-0.5*$height,
						$i*$rh-0.5*$width, $height/2,
						$width/2,1.5*$height-$i*$rw,
						1.5*$width-$i*$rh, $height/2 ), 4, $fill);
					break;
				default:	
			}		
		}
	}
	
	// #ff00ff -> array(255,0,255) or #f0f -> array(255,0,255)
	function hex2rgb($color) {
		$color = str_replace('#','',$color);
		$s = strlen($color) / 3;
		$rgb[]=hexdec(str_repeat(substr($color,0,$s),2/$s));
		$rgb[]=hexdec(str_repeat(substr($color,$s,$s),2/$s));
		$rgb[]=hexdec(str_repeat(substr($color,2*$s,$s),2/$s));
		return $rgb;
	}
}
?>

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