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: 与 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` 现在需要 GdImage 实例；之前需要有效的 `gd` resource。
7.2.0	新增 `IMG_EFFECT_MULTIPLY`（要求系统 libgd >= 2.1.1 或捆绑 libgd）。

示例

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);
?>

以上示例的输出类似于：

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用户贡献的备注 4 notes

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rx ¶

10 years ago

IMG_EFFECT_OVERLAY doesn't work in PHP 5.6.0 with GD version: 2.1.0-alpha.

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andrew at iwebsolutions dot co dot uk ¶

16 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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-1

[myname] at mac dot com ¶

16 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);

?>

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-1

Remon ¶

16 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.