我想调整一个图像PNG的透明度，请帮助。下面是代码:
function resize($width,$height) {
$new_image = imagecreatetruecolor($width, $height);
imagealphablending($new_image, false);
imagesavealpha($new_image,true);
$transparent = imagecolorallocatealpha($new_image, 255, 255, 255, 127);
imagefilledrectangle($new_image, 0, 0, $width, $height, $transparent);
imagecopyresampled($new_image, $this->image, 0, 0, 0, 0, $width, $height, $this->getWidth(), $this->getHeight());
$this->image = $new_image;
}
试试这个
function createThumb($upfile, $dstfile, $max_width, $max_height){
$size = getimagesize($upfile);
$width = $size[0];
$height = $size[1];
$x_ratio = $max_width / $width;
$y_ratio = $max_height / $height;
if( ($width <= $max_width) && ($height <= $max_height)) {
$tn_width = $width;
$tn_height = $height;
} elseif (($x_ratio * $height) < $max_height) {
$tn_height = ceil($x_ratio * $height);
$tn_width = $max_width;
} else {
$tn_width = ceil($y_ratio * $width);
$tn_height = $max_height;
}
if($size['mime'] == "image/jpeg"){
$src = ImageCreateFromJpeg($upfile);
$dst = ImageCreateTrueColor($tn_width, $tn_height);
imagecopyresampled($dst, $src, 0, 0, 0, 0, $tn_width, $tn_height,$width, $height);
imageinterlace( $dst, true);
ImageJpeg($dst, $dstfile, 100);
} else if ($size['mime'] == "image/png"){
$src = ImageCreateFrompng($upfile);
// integer representation of the color black (rgb: 0,0,0)
$background = imagecolorallocate($src, 0, 0, 0);
// removing the black from the placeholder
imagecolortransparent($src, $background);
// turning off alpha blending (to ensure alpha channel information
// is preserved, rather than removed (blending with the rest of the
// image in the form of black))
imagealphablending($src, false);
// turning on alpha channel information saving (to ensure the full range
// of transparency is preserved)
imagesavealpha($src, true);
$dst = ImageCreateTrueColor($tn_width, $tn_height);
imagecopyresampled($dst, $src, 0, 0, 0, 0, $tn_width, $tn_height,$width, $height);
Imagepng($dst, $dstfile);
} else {
$src = ImageCreateFromGif($upfile);
$dst = ImageCreateTrueColor($tn_width, $tn_height);
imagecopyresampled($dst, $src, 0, 0, 0, 0, $tn_width, $tn_height,$width, $height);
imagegif($dst, $dstfile);
}
}
有一个简单易用的开源库叫做PHP图像魔术师。它使用GD并支持透明性
基数使用示例:
$magicianObj = new imageLib('racecar.png');
$magicianObj -> resizeImage(100, 200, 'crop');
$magicianObj -> saveImage('racecar_small.png');