imagecolorallocatealpha
(PHP 4 >= 4.3.2, PHP 5, PHP 7, PHP 8)
imagecolorallocatealpha — 為一幅影象分配顏色 + alpha
說明
imagecolorallocatealpha(
resource
int
int
int
int
): int
resource
$image,int
$red,int
$green,int
$blue,int
$alpha): int
imagecolorallocatealpha() 的行為和 imagecolorallocate() 相同，但多了一個額外的透明度參數 alpha，其值從 0 到 127。0 表示完全不透明，127 表示完全透明。
如果分配失敗則返回 false。
示例 #1 使用 imagecolorallocatealpha() 的例子
<?php
$size = 300;
$image=imagecreatetruecolor($size, $size);
// 用白色背景加黑色邊框畫個方框
$back = imagecolorallocate($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 值分配一些顏色
$yellow = imagecolorallocatealpha($image, 255, 255, 0, 75);
$red = imagecolorallocatealpha($image, 255, 0, 0, 75);
$blue = imagecolorallocatealpha($image, 0, 0, 255, 75);
// 畫三個交迭的圓
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, $blue);
// 不要忘記輸出正確的 header！
header('Content-type: image/png');
// 最後輸出結果
imagepng($image);
imagedestroy($image);
?> 參數
-
image 由圖像建立函式(例如imagecreatetruecolor())返回的 GdImage 對象。
-
red 紅色成分的值。
-
green 綠色成分的值。
-
blue 藍色成分的值。
-
alpha A value between
0and127.0indicates completely opaque while127indicates completely transparent.
返回值
A color identifier or false if the allocation failed.
更新日誌
| 版本 | 說明 |
|---|---|
| Prior to 5.1.3 | Returns -1 if the allocation failed. |
範例
示例 #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 circle
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, $blue);
// don't forget to output a correct header!
header('Content-Type: image/png');
// and finally, output the result
imagepng($image);
imagedestroy($image);
?> 以上例程的輸出類似於：
註釋
參見
- imagecolorallocate() - 為一幅影象分配顏色
- imagecolordeallocate() - 取消影象顏色的分配