Php/docs/function.imagecolorallocatealpha
imagecolorallocatealpha
(PHP 4 >= 4.3.2, PHP 5, PHP 7)
imagecolorallocatealpha — 为一幅图像分配颜色 + alpha
说明
imagecolorallocatealpha
( resource $image
, int $red
, int $green
, int $blue
, int $alpha
) : int
imagecolorallocatealpha() 的行为和
imagecolorallocate() 相同,但多了一个额外的透明度参数
alpha
,其值从
0
到 127
。0
表示完全不透明,127
表示完全透明。
如果分配失败则返回 false
。
Example #1 使用 imagecolorallocatealpha() 的例子
<?php$size = 300;$image=imagecreatetruecolor($size, $size);// 用白色背景加黑色边框画个方框$back = imagecolorallocate($image, 255, 255, 255);$border = imagecolorallocate($image, 0, 0, 0);imagefilledrectangle($image, 0, 0, $size - 1, $size - 1, $back);imagerectangle($image, 0, 0, $size - 1, $size - 1, $border);$yellow_x = 100;$yellow_y = 75;$red_x = 120;$red_y = 165;$blue_x = 187;$blue_y = 125;$radius = 150;// 用 alpha 值分配一些颜色$yellow = imagecolorallocatealpha($image, 255, 255, 0, 75);$red = imagecolorallocatealpha($image, 255, 0, 0, 75);$blue = imagecolorallocatealpha($image, 0, 0, 255, 75);// 画三个交迭的圆imagefilledellipse($image, $yellow_x, $yellow_y, $radius, $radius, $yellow);imagefilledellipse($image, $red_x, $red_y, $radius, $radius, $red);imagefilledellipse($image, $blue_x, $blue_y, $radius, $radius, $blue);// 不要忘记输出正确的 header!header('Content-type: image/png');// 最后输出结果imagepng($image);imagedestroy($image);?>
参见 imagecolorallocate() 和 imagecolordeallocate()。
参数
image
- 由图象创建函数(例如imagecreatetruecolor())返回的图象资源。
red
- 红色成分的值。
green
- 绿色成分的值。
blue
- 蓝色成分的值。
alpha
- A value between
0
and127
.0
indicates completely opaque while127
indicates completely transparent.
The colors parameters are integers between 0 and 255 or hexadecimals between 0x00 and 0xFF.
返回值
A color identifier or false
if the allocation failed.
更新日志
版本 | 说明 |
---|---|
Prior to 5.1.3 | Returns -1 if the allocation failed. |
范例
Example #2 Example of using imagecolorallocatealpha()
<?php$size = 300;$image=imagecreatetruecolor($size, $size);// something to get a white background with black border$back = imagecolorallocate($image, 255, 255, 255);$border = imagecolorallocate($image, 0, 0, 0);imagefilledrectangle($image, 0, 0, $size - 1, $size - 1, $back);imagerectangle($image, 0, 0, $size - 1, $size - 1, $border);$yellow_x = 100;$yellow_y = 75;$red_x = 120;$red_y = 165;$blue_x = 187;$blue_y = 125;$radius = 150;// allocate colors with alpha values$yellow = imagecolorallocatealpha($image, 255, 255, 0, 75);$red = imagecolorallocatealpha($image, 255, 0, 0, 75);$blue = imagecolorallocatealpha($image, 0, 0, 255, 75);// drawing 3 overlapped circleimagefilledellipse($image, $yellow_x, $yellow_y, $radius, $radius, $yellow);imagefilledellipse($image, $red_x, $red_y, $radius, $radius, $red);imagefilledellipse($image, $blue_x, $blue_y, $radius, $radius, $blue);// don't forget to output a correct header!header('Content-Type: image/png');// and finally, output the resultimagepng($image);imagedestroy($image);?>
以上例程的输出类似于: