本文主要介绍了php实现对png图像进行缩放的方法(支持透明背景)，可实现php针对png图像的缩放功能,且支持透明背景，具有一定参考借鉴价值。希望对大家有所帮助。
具体实现方法如下：
function smart_resize_image( $file, $width = 0, $height = 0, $proportional = false, $output = 'file', $delete_original = true, $use_linux_commands = false )
{
if ( $height <= 0 && $width <= 0 ) {
return false;
}
$info = getimagesize($file);
$image = '';
$final_width = 0;
$final_height = 0;
list($width_old, $height_old) = $info;
if ($proportional) {
if ($width == 0) $factor = $height/$height_old;
elseif ($height == 0) $factor = $width/$width_old;
else $factor = min ( $width / $width_old, $height / $height_old);
$final_width = round ($width_old * $factor);
$final_height = round ($height_old * $factor);
}
else {
$final_width = ( $width <= 0 ) ? $width_old : $width;
$final_height = ( $height <= 0 ) ? $height_old : $height;
}
switch ($info[2] ) {
case imagetype_gif:
$image = imagecreatefromgif($file);
break;
case imagetype_jpeg:
$image = imagecreatefromjpeg($file);
break;
case imagetype_png:
$image = imagecreatefrompng($file);
break;
default:
return false;
}
$image_resized = imagecreatetruecolor( $final_width, $final_height );
if ( ($info[2] == imagetype_gif) || ($info[2] == imagetype_png) ) {
$trnprt_indx = imagecolortransparent($image);
// if we have a specific transparent color
if ($trnprt_indx >= 0) {
// get the original image's transparent color's rgb values
$trnprt_color = imagecolorsforindex($image, $trnprt_indx);
// allocate the same color in the new image resource
$trnprt_indx = imagecolorallocate($image_resized, $trnprt_color['red'], $trnprt_color['green'], $trnprt_color['blue']);
// completely fill the background of the new image with allocated color.
imagefill($image_resized, 0, 0, $trnprt_indx);
// set the background color for new image to transparent
imagecolortransparent($image_resized, $trnprt_indx);
}
// always make a transparent background color for pngs that don't have one allocated already
elseif ($info[2] == imagetype_png) {
// turn off transparency blending (temporarily)
imagealphablending($image_resized, false);
// create a new transparent color for image
$color = imagecolorallocatealpha($image_resized, 0, 0, 0, 127);
// completely fill the background of the new image with allocated color.
imagefill($image_resized, 0, 0, $color);
// restore transparency blending
imagesavealpha($image_resized, true);
}
}
imagecopyresampled($image_resized, $image, 0, 0, 0, 0, $final_width, $final_height, $width_old, $height_old);
if ( $delete_original ) {
if ( $use_linux_commands )
exec('rm '.$file);
else
@unlink($file);
}
switch ( strtolower($output) ) {
case 'browser':
$mime = image_type_to_mime_type($info[2]);
header("content-type: $mime");
$output = null;
break;
case 'file':
$output = $file;
break;
case 'return':
return $image_resized;
break;
default:
break;
}
switch ($info[2] ) {
case imagetype_gif:
imagegif($image_resized, $output);
break;
case imagetype_jpeg:
imagejpeg($image_resized, $output);
break;
case imagetype_png:
imagepng($image_resized, $output);
break;
default:
return false;
}
return true;
}
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以上就是php实现支持透明的png图像缩放的详细内容。