Question

我使用的以下代码是将源png合并到具有50％不透明度的目标png，以使其看起来像缝合。代码工作正常，但合并功能也将文件合并到目标的透明区域。有没有办法将源合并到非透明区域？

<?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 );
?>

Answer 1

imagecopymerge函数从未打算支持alpha通道。希望它可以帮助某人：

<?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。

Answer 2

来自php开发人员的另一个解决方案（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：对PHP Manual - imagecopymerge的评论。

如何使用PHP imagecopymerge（）将源文件合并到目的地的非透明区域？

2 个答案: