我使用下面的代码是合并源png到目标png 50%的不透明度，使其看起来缝合。代码工作得很好，但是merge函数也将文件合并到目标的透明区域。是否有任何方法来合并源到不透明的区域?
<?php
$src = imagecreatefrompng( 'http://dev.syntrio.in/arshad/project/test/texture.png' );
$dst = imagecreatefrompng( 'https://upload.wikimedia.org/wikipedia/en/3/34/Gmail_Logo.png' );
$w = imagesx( $dst );
$h = imagesy( $dst );
header( 'Content-type: image/png' );
imagealphablending($dst, false);
imagesavealpha($dst, true);
imagecopymerge( $dst, $src, 0, 0, 0, 0, $w, $h, 50 );
imagepng( $dst );
imagedestroy( $src );
imagedestroy( $dst );
?>
imagecopymerge函数从未打算支持alpha通道。希望能帮到别人:
<?php
/**
* PNG ALPHA CHANNEL SUPPORT for imagecopymerge();
* by Sina Salek
*
* Bugfix by Ralph Voigt (bug which causes it
* to work only for $src_x = $src_y = 0.
* Also, inverting opacity is not necessary.)
* 08-JAN-2011
*
**/
function imagecopymerge_alpha($dst_im, $src_im, $dst_x, $dst_y, $src_x, $src_y, $src_w, $src_h, $pct){
// creating a cut resource
$cut = imagecreatetruecolor($src_w, $src_h);
// copying relevant section from background to the cut resource
imagecopy($cut, $dst_im, 0, 0, $dst_x, $dst_y, $src_w, $src_h);
// copying relevant section from watermark to the cut resource
imagecopy($cut, $src_im, 0, 0, $src_x, $src_y, $src_w, $src_h);
// insert cut resource to destination image
imagecopymerge($dst_im, $cut, $dst_x, $dst_y, 0, 0, $src_w, $src_h, $pct);
}
?>
来源:PHP Manual - imagecopymerge.
另一个php开发人员的解决方案(占用更少的内存，但速度更慢)
<?php
/**
* PNG ALPHA CHANNEL SUPPORT for imagecopymerge();
* This is a function like imagecopymerge but it handle alpha channel well!!!
**/
// A fix to get a function like imagecopymerge WITH ALPHA SUPPORT
// Main script by aiden dot mail at freemail dot hu
// Transformed to imagecopymerge_alpha() by rodrigo dot polo at gmail dot com
function imagecopymerge_alpha($dst_im, $src_im, $dst_x, $dst_y, $src_x, $src_y, $src_w, $src_h, $pct){
if(!isset($pct)){
return false;
}
$pct /= 100;
// Get image width and height
$w = imagesx( $src_im );
$h = imagesy( $src_im );
// Turn alpha blending off
imagealphablending( $src_im, false );
// Find the most opaque pixel in the image (the one with the smallest alpha value)
$minalpha = 127;
for( $x = 0; $x < $w; $x++ )
for( $y = 0; $y < $h; $y++ ){
$alpha = ( imagecolorat( $src_im, $x, $y ) >> 24 ) & 0xFF;
if( $alpha < $minalpha ){
$minalpha = $alpha;
}
}
//loop through image pixels and modify alpha for each
for( $x = 0; $x < $w; $x++ ){
for( $y = 0; $y < $h; $y++ ){
//get current alpha value (represents the TANSPARENCY!)
$colorxy = imagecolorat( $src_im, $x, $y );
$alpha = ( $colorxy >> 24 ) & 0xFF;
//calculate new alpha
if( $minalpha !== 127 ){
$alpha = 127 + 127 * $pct * ( $alpha - 127 ) / ( 127 - $minalpha );
} else {
$alpha += 127 * $pct;
}
//get the color index with new alpha
$alphacolorxy = imagecolorallocatealpha( $src_im, ( $colorxy >> 16 ) & 0xFF, ( $colorxy >> 8 ) & 0xFF, $colorxy & 0xFF, $alpha );
//set pixel with the new color + opacity
if( !imagesetpixel( $src_im, $x, $y, $alphacolorxy ) ){
return false;
}
}
}
// The image copy
imagecopy($dst_im, $src_im, $dst_x, $dst_y, $src_x, $src_y, $src_w, $src_h);
}
// USAGE EXAMPLE:
$img_a = imagecreatefrompng('image1.png');
$img_b = imagecreatefrompng('wm2.png');
// SAME COMMANDS:
imagecopymerge_alpha($img_a, $img_b, 10, 10, 0, 0, imagesx($img_b), imagesy($img_b),50);
// OUTPUT IMAGE:
header("Content-Type: image/png");
imagesavealpha($img_a, true);
imagepng($img_a, NULL);
?>
来源:PHP手册- imagecopymerge注释