PHP: imagecolorallocatealpha - Manual

downloads | documentation | faq | getting help | mailing lists | reporting bugs | php.net sites | links | conferences | my php.net

search for in the

imagecolorat imagecolorallocate

Last updated: Sat, 27 Jan 2007

view this page in

# imagecolorallocatealpha

(PHP 4 >= 4.3.2, PHP 5)

imagecolorallocatealpha -- Allocate a color for an image

## Описание

int imagecolorallocatealpha ( resource image, int red, int green, int blue, int alpha )

imagecolorallocatealpha() behaves identically to imagecolorallocate() with the addition of the transparency parameter `alpha`.

## Список параметров

`image`

  An image resource, returned by one of the image creation functions, such as imagecreatetruecolor().

`red`

  Value of red component

`green`

  Value of green component

`blue`

  Value of blue component

`alpha`

  A value between `0` and `127`. `0` indicates completely opaque while `127` indicates completely transparent.

The colors parameters are integers between 0 and 255 or hexadecimals between 0x00 and 0xFF.

## Возвращаемые значения

A color identifier or `FALSE` if the allocation failed.

## Список изменений

Версия | Описание
--- | ---
Prior to 5.1.3 | Returns -1 if the allocation failed.

## Примеры

Пример 1. 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);
?>`

Результатом выполнения данного примера будет что-то подобное:

## Примечания

> Замечание: Эта функция нуждается в GD версии 2.0.1 или выше.

## Смотрите также

imagecolorallocate()
imagecolordeallocate()

add a note User Contributed Notes
imagecolorallocatealpha
eric (at) junioronline.us
25-Jan-2006 01:41
`If you only wish to extract the alpha value for a color, you can simply extract it like so:
<?php
$color = imagecolorat($im, 50, 50);
$alpha = $color >> 24;
?>
It actually shifts off the first 24 bits (where 8x3 are used for each color), and returns the remaining 7 allocated bits (commonly used for alpha)`
fchristl at hotmail dot com
19-Sep-2003 12:55
`Check out this Source, it's a little funny feature showing you, for what imagecolorallocatealpha() is used:
<?php
$im=imagecreatetruecolor(300,300);
$white=imagecolorallocate($im,255,255,255);
imagefilledrectangle($im,0,0,imagesx($im),imagesy($im),$white);
for($i=0;$i<256;$i=$i+10)
{
$col=imagecolorallocatealpha($im,$i,$i,$i,ceil(rand(0,127)));
imagefilledellipse($im,$i,$i,$i,$i,$col);
}
header("content-type: image/png");
imagepng($im);
?>`
add a note
imagecolorat imagecolorallocate

Last updated: Sat, 27 Jan 2007
show source | credits | stats | sitemap | contact | advertising | mirror sites
Copyright © 2001-2007 The PHP Group
All rights reserved.
This mirror generously provided by: Yahoo! Inc.
Last updated: Sat Mar 10 09:32:46 2007 PST