imagelayereffect

(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)

imagelayereffect设定 alpha 混合标志以使用分层效果

说明

imagelayereffect(GdImage $image, int $effect): bool

设定 alpha 混色标志以使用分层效果。

参数

image

由图象创建函数(例如imagecreatetruecolor())返回的 GdImage 对象。

effect

下列常量之一:

IMG_EFFECT_REPLACE
使用像素替换(等同于将 true 传递给 imagealphablending()
IMG_EFFECT_ALPHABLEND
使用普通像素混合(等同于将 false 传递给 imagealphablending()
IMG_EFFECT_NORMAL
IMG_EFFECT_ALPHABLEND 相同。
IMG_EFFECT_OVERLAY
叠加(overlay)的效果是黑色背景像素将保持黑色,白色背景像素将保持白色,但灰色背景像素将采用前景像素的颜色。
IMG_EFFECT_MULTIPLY
Overlays with a multiply effect.

返回值

成功时返回 true, 或者在失败时返回 false

更新日志

版本 说明
8.0.0 image expects a GdImage instance now; previously, a resource was expected.
7.2.0 新增 IMG_EFFECT_MULTIPLY(要求系统 libgd >= 2.1.1 或捆绑 libgd)。

范例

示例 #1 imagelayereffect() 示例

<?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:

示例输出:imagelayereffect()
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User Contributed Notes 4 notes

up
0
rx
8 years ago
IMG_EFFECT_OVERLAY doesn't work in PHP 5.6.0 with GD version: 2.1.0-alpha.
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0
[myname] at mac dot com
14 years ago
^^ 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);

?>
up
0
Remon
14 years ago
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.
up
-2
andrew at iwebsolutions dot co dot uk
14 years ago
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.
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