php imagecreatefrompng() 制作黑色背景而不是透明背景？
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imagecreatefrompng() Makes a black background instead of transparent?
提问by Emily
I make thumbnails using PHP and GD library but my code turn png transparency into a solid black color, Is there a solution to improve my code?
我使用 PHP 和 GD 库制作缩略图，但我的代码将 png 透明度变成纯黑色，是否有改进我的代码的解决方案？
this is my php thumbnail maker code:
这是我的 php 缩略图制作器代码：
function cropImage($nw, $nh, $source, $stype, $dest) {
$size = getimagesize($source);
$w = $size[0];
$h = $size[1];
switch($stype) {
case 'gif':
$simg = imagecreatefromgif($source);
break;
case 'jpg':
$simg = imagecreatefromjpeg($source);
break;
case 'png':
$simg = imagecreatefrompng($source);
break;
}
$dimg = imagecreatetruecolor($nw, $nh);
$wm = $w/$nw;
$hm = $h/$nh;
$h_height = $nh/2;
$w_height = $nw/2;
if($w> $h) {
$adjusted_width = $w / $hm;
$half_width = $adjusted_width / 2;
$int_width = $half_width - $w_height;
imagecopyresampled($dimg,$simg,-$int_width,0,0,0,$adjusted_width,$nh,$w,$h);
} elseif(($w <$h) || ($w == $h)) {
$adjusted_height = $h / $wm;
$half_height = $adjusted_height / 2;
$int_height = $half_height - $h_height;
imagecopyresampled($dimg,$simg,0,-$int_height,0,0,$nw,$adjusted_height,$w,$h);
} else {
imagecopyresampled($dimg,$simg,0,0,0,0,$nw,$nh,$w,$h);
}
imagejpeg($dimg,$dest,100);
}
Thank you
谢谢
回答by Adrian
After imagecreatetruecolor():
在 imagecreatetruecolor() 之后：
<?php
// ... Before imagecreatetruecolor()
$dimg = imagecreatetruecolor($width_new, $height_new); // png ?: gif
// start changes
switch ($stype) {
case 'gif':
case 'png':
// integer representation of the color black (rgb: 0,0,0)
$background = imagecolorallocate($dimg , 0, 0, 0);
// removing the black from the placeholder
imagecolortransparent($dimg, $background);
// turning off alpha blending (to ensure alpha channel information
// is preserved, rather than removed (blending with the rest of the
// image in the form of black))
imagealphablending($dimg, false);
// turning on alpha channel information saving (to ensure the full range
// of transparency is preserved)
imagesavealpha($dimg, true);
break;
default:
break;
}
// end changes
$wm = $w/$nw;
$hm = $h/$nh;
// ...
回答by Yahia Mgarrech
if the code of the correct answer don't work try this :
如果正确答案的代码不起作用，请尝试以下操作：
//After imagecreatetruecolor():
$white = imagecolorallocate($dimg, 255, 255, 255);
imagefill($dimg,0,0,$white);
回答by pgee70
The order of operations is important. for .gif images i found that i needed to copy resized image first, then assign the black background as transparent. for PNGs I found the code below resized images and kept the transparency backgrounds.
操作顺序很重要。对于 .gif 图像，我发现我需要先复制调整大小的图像，然后将黑色背景指定为透明。对于 PNG，我发现下面的代码调整了图像大小并保留了透明背景。
also, this code worked for me...
另外，这段代码对我有用......
$resized_image = imagecreatetruecolor($target_width, $target_height);
switch ( $asset->a_mime_type )
{
case 'image/jpeg':
imagecopyresampled($resized_image, $source, 0, 0, 0, 0, $target_width, $target_height, $asset->a_image_width, $asset->a_image_height);
$r = imagejpeg($resized_image,$file_name);
break;
case 'image/png':
imagealphablending($resized_image, FALSE);
imagesavealpha($resized_image, TRUE);
imagecopyresampled($resized_image, $source, 0, 0, 0, 0, $target_width, $target_height, $asset->a_image_width, $asset->a_image_height);
$r = @imagepng($resized_image,$file_name);
break;
case 'image/gif':
imagecopyresampled($resized_image, $source, 0, 0, 0, 0, $target_width, $target_height, $asset->a_image_width, $asset->a_image_height);
$background = imagecolorallocate($resized_image, 0, 0, 0);
imagecolortransparent($resized_image, $background);
$r = @imagegif($resized_image,$file_name);
break;
}
回答by Stone
Sometimes if the .jpg image got small errors inside (you cannot see that), all transparent pixels turn to black color.Try to use:
有时，如果 .jpg 图像内部出现小错误（您看不到），则所有透明像素都会变为黑色。尝试使用：
ini_set('gd.jpeg_ignore_warning', 1);
回答by Md. Imadul Islam
Here is my total test code. It works for me
这是我的总测试代码。这个对我有用
$imageFileType = pathinfo($_FILES["image"]["name"], PATHINFO_EXTENSION);
$filename = 'test.' . $imageFileType;
move_uploaded_file($_FILES["image"]["tmp_name"], $filename);
$source_image = imagecreatefromjpeg($filename);
$source_imagex = imagesx($source_image);
$source_imagey = imagesy($source_image);
$dest_imagex = 400;
$dest_imagey = 600;
$dest_image = imagecreatetruecolor($dest_imagex, $dest_imagey);
imagecopyresampled($dest_image, $source_image, 0, 0, 0, 0, $dest_imagex, $dest_imagey, $source_imagex, $source_imagey);
imagesavealpha($dest_image, true);
$trans_colour = imagecolorallocatealpha($dest_image, 0, 0, 0, 127);
imagefill($dest_image, 0, 0, $trans_colour);
imagepng($dest_image,"test1.png",1);
回答by Aba
Some of the above made the black parts of the image turn white, while some didn't work at all. This, however, worked for me https://github.com/claviska/SimpleImage/issues/28
上面的一些使图像的黑色部分变成白色，而有些则根本不起作用。然而，这对我有用 https://github.com/claviska/SimpleImage/issues/28
回答by Basit
change rgb to 255, it will give you transparent image, rather then black.
将 rgb 更改为 255，它将为您提供透明图像，而不是黑色。
<?php
switch ($stype)
{
case "png":
// integer representation of the color black (rgb: 0,0,0)
$background = imagecolorallocate($simage, 255, 255, 255);
// removing the black from the placeholder
imagecolortransparent($simage, $background);
// turning off alpha blending (to ensure alpha channel information is preserved, rather than removed (blending with the rest of the image in the form of black))
imagealphablending($simage, false);
// turning on alpha channel information saving (to ensure the full range of transparency is preserved)
imagesavealpha($simage, true);
break;
case "gif":
// integer representation of the color black (rgb: 0,0,0)
$background = imagecolorallocate($simage, 255, 255, 255);
// removing the black from the placeholder
imagecolortransparent($simage, $background);
break;
}
?>
