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,$startcolor,$endcolor,$step); gd_gradient_fill有5个必要参数和一个可选参数:
- integer $width
Width of the image - integer $height
Height of the image - string $direction
The shape or direction of the gradient, which can be any of : vertical, horizontal, ellipse, ellipse2, circle, circle2, rectangle, diamond. - string $startcolor
Gradient start color, 3 or 6 digit hexadecimal ("#ff0" or "#dd4578") - string $endcolor
Gradient end color - 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:
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 < $line_numbers; $i=$i+1+$this->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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