我正在尝试在 php 手册中实现用户提供的示例代码，但它没有按预期运行

Question

我正在尝试在 PHP 手册的这一页上实现 killing_wombles0000（8 年前）提供的代码：https://www.php.net/manual/en/function.imagecopymerge.php 问题是代码中存在错误/意外行为（例如，$a 未定义）它有点工作，但是镜像图像逐渐变成白色，我希望它逐渐变成黑色。当我做出我认为需要的改变时，我无法按照我的意愿去做。代码中有太多我不熟悉的图像函数，我无法理解它们的协同工作。

我花了一整天的时间阅读每个函数，尝试按逻辑处理代码、注释掉部分内容、更改透明度颜色以及通常抓紧稻草。我认为将出现的 255,255,255 更改为 0,0,0 会使镜像图像淡化为黑色。我真天真 ;)

这是用户在 PHP 手册的该页上提供的代码：

$in = imagecreatefromjpeg('C:\test.jpg');
$reflection_strength = 120;        //    starting transparency (0-127, 0 being opaque)
$reflection_height = 40;        //     height of reflection in pixels
$gap = 10;                        //    gap between image and reflection

$orig_height = imagesy($in);                                //    store height of original image
$orig_width = imagesx($in);                                    //    store height of original image
$output_height = $orig_height + $reflection_height + $gap;    //    calculate height of output image

// create new image to use for output. fill with transparency. ALPHA BLENDING MUST BE FALSE
$out = imagecreatetruecolor($orig_width, $output_height);
imagealphablending($out, false);
$bg = imagecolortransparent($out, imagecolorallocatealpha($out, 255, 255, 255, 127));
imagefill($out, 0, 0, $bg);
imagefilledrectangle($out, 0, 0, imagesx($in), imagesy($in), $bg1);

// copy original image onto new one, leaving space underneath for reflection and 'gap'
imagecopyresampled ( $out , $in , 0, 0, 0, 0, imagesx($in), imagesy($in), imagesx($in), imagesy($in));

 // create new single-line image to act as buffer while applying transparency
$reflection_section = imagecreatetruecolor(imagesx($in), 1);
imagealphablending($reflection_section, false);
$bg1 = imagecolortransparent($reflection_section, imagecolorallocatealpha($reflection_section, 255, 255, 255, 127));
imagefill($reflection_section, 0, 0, $bg1);

// 1. copy each line individually, starting at the 'bottom' of the image, working upwards.
// 2. set transparency to vary between reflection_strength and 127
// 3. copy line back to mirrored position in original
for ($y = 0; $y<$reflection_height;$y++)
{   
    $t = ((127-$reflection_strength) + ($reflection_strength*($y/$reflection_height)));
    imagecopy($reflection_section, $out, 0, 0, 0, imagesy($in)  - $y, imagesx($in), 1);
    imagefilter($reflection_section, IMG_FILTER_COLORIZE, 0, 0, 0, $t);
    imagecopyresized($out, $reflection_section, $a, imagesy($in) + $y + $gap, 0, 0, imagesx($in) - (2*$a), 1, imagesx($in), 1);
}

// output image to view
header('Content-type: image/png');
imagesavealpha($out,true);
imagepng($out);

在循环进入之前将 $a 设置为 0 可消除错误。

Answer 1

您发现的代码中似乎存在一些错误。

$bg1 没有为主输出图像定义。我在 imagefilledrectangle.

$bg1

$bg

$a 未定义。我将对 $a 的引用更改为零，因为它引用了一个 "x" 坐标，我们想要图像的整个宽度，从零到它的全宽度。

反射部分逐渐变透明。由于页面的颜色是白色，图像看起来像是褪色成白色。如果你想淡化成黑色而不是透明，我建议保留默认的混合模式，这样背景颜色就会透出来，并将背景颜色设置为黑色：

//imagealphablending($out, false);
//$bg = imagecolortransparent($out, imagecolorallocatealpha($out, 255, 255, 255, 127));
$bg = imagecolorallocatealpha($out, 0,0,0,0);

参考 imagealphablending。

这是一个例子：

$in = imagecreatefromjpeg('https://picsum.photos/id/1084/536/354?grayscale');
$reflection_strength = 127;        //    starting transparency (0-127, 0 being opaque)
$reflection_height = 40;        //     height of reflection in pixels
$gap = 0;                        //    gap between image and reflection

$orig_height = imagesy($in);                                //    store height of original image
$orig_width = imagesx($in);                                    //    store height of original image
$output_height = $orig_height + $reflection_height + $gap;    //    calculate height of output image

// create new image to use for output. fill with BLACK.
$out = imagecreatetruecolor($orig_width, $output_height);
//imagealphablending($out, false);
//$bg = imagecolortransparent($out, imagecolorallocatealpha($out, 255, 255, 255, 127));
$bg = imagecolorallocatealpha($out, 0,0,0,0);
imagefill($out, 0, 0, $bg);
imagefilledrectangle($out, 0, 0, imagesx($in), imagesy($in), $bg);

// copy original image onto new one, leaving space underneath for reflection and 'gap'
imagecopyresampled ( $out , $in , 0, 0, 0, 0, imagesx($in), imagesy($in), imagesx($in), imagesy($in));

 // create new single-line image to act as buffer while applying transparency
$reflection_section = imagecreatetruecolor(imagesx($in), 1);
imagealphablending($reflection_section, false);
$bg1 = imagecolortransparent($reflection_section, imagecolorallocatealpha($reflection_section, 255, 255, 255, 127));
imagefill($reflection_section, 0, 0, $bg1);

// 1. copy each line individually, starting at the 'bottom' of the image, working upwards.
// 2. set transparency to vary between reflection_strength and 127
// 3. copy line back to mirrored position in original
for ($y = 0; $y<$reflection_height;$y++)
{
    $t = ((127-$reflection_strength) + ($reflection_strength*($y/$reflection_height)));
    imagecopy($reflection_section, $out, 0, 0, 0, imagesy($in)  - $y, imagesx($in), 1);
    imagefilter($reflection_section, IMG_FILTER_COLORIZE, 0, 0, 0, $t);
    imagecopyresized($out, $reflection_section, 0, imagesy($in) + $y + $gap, 0, 0, imagesx($in) - 0, 1, imagesx($in), 1);
}

// output image to view
header('Content-type: image/png');
imagesavealpha($out,true);
imagepng($out);

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我正在尝试在 php 手册中实现用户提供的示例代码，但它没有按预期运行

I'm trying to implement user-supplied example code in the php manual but it doesn't behave as expected

php

image-processing

mirroring