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php缩小png图片不损失透明色的解决方法_PHP

WBOY
WBOYOriginal
2016-06-01 11:58:071134browse

主要是利用gd库的两个方法:
复制代码 代码如下:
imagecolorallocatealpha //分配颜色 + alpha

imagesavealpha //设置在保存 png 图像时保存完整的 alpha 通道信息

代码示例:

复制代码 代码如下:
//获取源图gd图像标识符
$srcImg = imagecreatefrompng('./src.png');
$srcWidth = imagesx($srcImg);
$srcHeight = imagesy($srcImg);

//创建新图
$newWidth = round($srcWidth / 2);
$newHeight = round($srcHeight / 2);
$newImg = imagecreatetruecolor($newWidth, $newHeight);
//分配颜色 + alpha,将颜色填充到新图上
$alpha = imagecolorallocatealpha($newImg, 0, 0, 0, 127);
imagefill($newImg, 0, 0, $alpha);

//将源图拷贝到新图上,并设置在保存 PNG 图像时保存完整的 alpha 通道信息
imagecopyresampled($newImg, $srcImg, 0, 0, 0, 0, $newWidth, $newHeight, $srcWidth, $srcHeight);
imagesavealpha($newImg, true);
imagepng($newImg, './dst.png');

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