ImageCopy输出颜色

Question

我尝试使用php合并两个图像。我做了之后，输出颜色与原点不一样。 我的代码怎么了？

图片1

图片2

输出

这是我的代码

$top_file = '1.png';
$bottom_file = '2.png';
$top = imagecreatefrompng($top_file);
$bottom = imagecreatefrompng($bottom_file);

// get current width/height
list($top_width, $top_height) = getimagesize($top_file);
list($bottom_width, $bottom_height) = getimagesize($bottom_file);

// compute new width/height
$new_width = ($top_width > $bottom_width) ? $top_width : $bottom_width;
$new_height = $top_height + $bottom_height;

// create new image and merge
$new = imagecreate($new_width, $new_height);
imagecopy($new, $top, 0, 0, 0, 0, $top_width, $top_height);
imagecopy($new, $bottom, 0, $top_height+1, 0, 0, $bottom_width, $bottom_height);

// save to file
imagepng($new, 'merged_image.png');

Answer 1

作为@Niet，Dark Absol说，你需要imagecreatetruecolor而不是imagecreate。但是，您需要更多步骤来保持透明度。主要功能包括imagesavealpha和imagefill。前者保留透明度，后者为新创建的图像提供透明背景。这是一份工作副本：

$top_file = '1.png';
$bottom_file = '2.png';
$top = imagecreatefrompng($top_file);
$bottom = imagecreatefrompng($bottom_file);

// get current width/height
list($top_width, $top_height) = getimagesize($top_file);
list($bottom_width, $bottom_height) = getimagesize($bottom_file);

// compute new width/height
$new_width = ($top_width > $bottom_width) ? $top_width : $bottom_width;
$new_height = $top_height + $bottom_height;

// create new image and merge
$new = imagecreatetruecolor($new_width, $new_height);
imagesavealpha($new, true);

$trans_colour = imagecolorallocatealpha($new, 0, 0, 0, 127);
imagefill($new, 0, 0, $trans_colour);

imagecopy($new, $top, 0, 0, 0, 0, $top_width, $top_height);
imagecopy($new, $bottom, 0, $top_height+1, 0, 0, $bottom_width, $bottom_height);

// save to file
imagepng($new, 'merged_image.png');

Answer 2

使用imagecreate创建的图像是基于调色板的，因此限制为256色。你有高度渐变的图像。请改用imagecreatetruecolor。