Facebook风格上传的图片大小调整和压缩

Question

Facebook会调整我们上传的图像的大小，如果它高于2 megapixels。比如我的图片是3264x1832，facebook将其调整为2048x1529。那么，如果它是长边，图片会减少到2048px。缩小是测量另一个边缘缩小到的程度。之后，针对图像大小进行图像压缩。该方法在大图像中非常小心。我将做我的mvc 5项目的方法，如何找到一个c#、jquery、javascrip、php插件或类似的api方法？

Answer 1

这需要在php服务器上安装GD，并期望path/to/temp/image.jpg是上传图像的位置。如果上传了不支持的文件类型或损坏的图像，您可能需要使用try/catch。

以下是主要程序代码：

$maxWidth = 2048;
$maxHeight = 2048;
$compression = 75;
//Create an image object out of the uploaded file
$sourceImage = imagecreatefromjpeg('path/to/temp/image.jpg'); 
//Resize the image
$resizedImage = ImageSizeDown($sourceImage, $maxWidth, $maxHeight);
//Save the image as a jpeg to it's new home
imagejpeg($resizedImage, 'path/to/permanent/image.jpg', $compression);

这些是额外的必要功能：

//Function for resizing an image if it's larger than a certain resolution
function ImageSizeDown($image, $maxWidth, $maxHeight) {
    $maxAspect = $maxWidth / $maxHeight;
    $sourceWidth = imagesx($image);
    $sourceHeight = imagesy($image);
    $sourceAspect = $sourceWidth / $sourceHeight;
    if($sourceWidth > $maxWidth || $sourceHeight > $maxHeight) {
        if($maxAspect > $sourceAspect) {
            $newWidth = (int)$maxWidth;
            $newHeight = (int)($maxWidth / $sourceWidth * $sourceHeight);
        }
        else { 
            $newHeight = (int)$maxHeight;
            $newWidth = (int)($maxHeight / $sourceHeight * $sourceWidth);
        }
        $result = TransparentImage($newWidth, $newHeight);
        imagesavealpha($image, true);
        imagealphablending($image, false);
        imagecopyresampled($result, $image, 0, 0, 0, 0, $newWidth, $newHeight, $sourceWidth, $sourceHeight);
        return $result;
    }
    else return $image; //Image is already small enough
}
//Handy function for creating a base for most any image stuff, especially PNG
function TransparentImage($x, $y) { 
    $image = imagecreatetruecolor($x, $y);
    imagesavealpha($image, true);
    imagealphablending($image, false);
    $transparent = imagecolorallocatealpha($image, 200, 200, 200, 127);
    imagefill($image, 0, 0, $transparent);
    return $image;
}

我现在不在任何地方可以测试这个，所以我的纵横比数学可能会被转换。