IMG_EFFECT_OVERLAY doesn't work in PHP 5.6.0 with GD version: 2.1.0-alpha.
imagelayereffect
(PHP 4 >= 4.3.0, PHP 5, PHP 7)
imagelayereffect — 设定 alpha 混色标志以使用绑定的 libgd 分层效果
说明
imagelayereffect
( resource
$image
, int $effect
) : bool设定 alpha 混色标志以使用绑定的 libgd 分层效果。
参数
-
image -
由图象创建函数(例如imagecreatetruecolor())返回的图象资源。
-
effect -
One of the following constants:
-
IMG_EFFECT_REPLACE -
Use pixel replacement (equivalent of passing
TRUEto imagealphablending()) -
IMG_EFFECT_ALPHABLEND -
Use normal pixel blending (equivalent of passing
FALSEto imagealphablending()) -
IMG_EFFECT_NORMAL -
Same as
IMG_EFFECT_ALPHABLEND. -
IMG_EFFECT_OVERLAY - Overlay has the effect that black background pixels will remain black, white background pixels will remain white, but grey background pixels will take the colour of the foreground pixel.
-
返回值
成功时返回 TRUE， 或者在失败时返回 FALSE。
范例
Example #1 imagelayereffect() example
<?php
// Setup an image
$im = imagecreatetruecolor(100, 100);
// Set a background
imagefilledrectangle($im, 0, 0, 100, 100, imagecolorallocate($im, 220, 220, 220));
// Apply the overlay alpha blending flag
imagelayereffect($im, IMG_EFFECT_OVERLAY);
// Draw two grey ellipses
imagefilledellipse($im, 50, 50, 40, 40, imagecolorallocate($im, 100, 255, 100));
imagefilledellipse($im, 50, 50, 50, 80, imagecolorallocate($im, 100, 100, 255));
imagefilledellipse($im, 50, 50, 80, 50, imagecolorallocate($im, 255, 100, 100));
// Output
header('Content-type: image/png');
imagepng($im);
imagedestroy($im);
?>
以上例程的输出类似于：
注释
Note: 此函数仅在与 GD 库捆绑编译的 PHP 版本中可用。
Note: 此函数需要 GD 2.0.1 或更高版本(推荐 2.0.28 及更高版本)。
User Contributed Notes
rx
23-Sep-2014 12:15
andrew at iwebsolutions dot co dot uk
07-Oct-2008 03:38
I have been getting a fatal error:
Fatal error: Call to undefined function imagelayereffect()
This doesn't work with Ubuntu server (8.04 lts) and the php5-gd package. If you need this you will have to recompile PHP with GD built-in.
[myname] at mac dot com
23-Feb-2008 11:45
^^ my name is coreyward ^^
imagelayereffect needs to be applied to the destination image, not the source image. As noted, the only useful "effect" as of this time is IMG_EFFECT_OVERLAY since the others are merely another way of setting the alpha blending flag.
You can also use imagecopymerge with a lower pct argument to blend two images with more control over the opacity at which the top image is blended.
<?
// overlays $im_src onto $im_dst properly (assuming same dims)
imagelayereffect($im_dst, IMG_EFFECT_OVERLAY);
imagecopy($im_dst, $im_src, 0, 0, 0, 0, $im_dst_x, $im_dst_y);
?>
Remon
05-Feb-2008 01:12
I found the following example on a Chinese site and translated and adjusted it. It creates a portrait from the sample picture.
<?php
// Portrait image
$im = imagecreatefromjpeg( "sample.jpg");
// Get width and height
$w = imagesx($im);
$h = imagesy($im);
// Non-through
$c_visible = 0x007F7F7F;
// Background (black)
$c_bg = 0x00000000;
// Create mask
$im_mask = imagecreatetruecolor($w,$h);
imageFilledRectangle($im_mask, 0,0, $w,$h, $c_bg);
imageFilledEllipse ($im_mask, $w/2,$h/2, $w*.9,$h*.9, $c_visible);
// Only overlay seems to something useful
imagelayereffect($im_mask, IMG_EFFECT_OVERLAY);
imagecopy($im_mask, $im, 0,0, 0,0, $w,$h);
imagedestroy($im);
imagepng($im_mask);
imagedestroy($im_mask);
?>
Try removing the 'create mask' code and just add another image with 'createimagefromjpeg' to see 'normal' overlay. It blends the colors like different layers in Photoshop.