PHP图片裁剪、缩放function

根据自定义的目标图高宽, 按目标图高宽比裁剪、缩放源图.

传入参数:

$source_path string 源图路径

$target_width integer 目标图宽度

$target_height integer 目标图高度

源图支持MIMETYPE: image/gif, image/jpeg, image/png.

function imagecropper($source_path, $target_width, $target_height)
{
    $source_info   = getimagesize($source_path);
    $source_width  = $source_info[0];
    $source_height = $source_info[1];
    $source_mime   = $source_info['mime'];
    $source_ratio  = $source_height / $source_width;
    $target_ratio  = $target_height / $target_width;

    // 源图过高
    if ($source_ratio > $target_ratio)
    {
        $cropped_width  = $source_width;
        $cropped_height = $source_width * $target_ratio;
        $source_x = 0;
        $source_y = ($source_height - $cropped_height) / 2;
    }
    // 源图过宽
    elseif ($source_ratio < $target_ratio)
    {
        $cropped_width  = $source_height / $target_ratio;
        $cropped_height = $source_height;
        $source_x = ($source_width - $cropped_width) / 2;
        $source_y = 0;
    }
    // 源图适中
    else
    {
        $cropped_width  = $source_width;
        $cropped_height = $source_height;
        $source_x = 0;
        $source_y = 0;
    }

    switch ($source_mime)
    {
        case 'image/gif':
            $source_image = imagecreatefromgif($source_path);
            break;

        case 'image/jpeg':
            $source_image = imagecreatefromjpeg($source_path);
            break;

        case 'image/png':
            $source_image = imagecreatefrompng($source_path);
            break;

        default:
            return false;
            break;
    }

    $target_image  = imagecreatetruecolor($target_width, $target_height);
    $cropped_image = imagecreatetruecolor($cropped_width, $cropped_height);

    // 裁剪
    imagecopy($cropped_image, $source_image, 0, 0, $source_x, $source_y, $cropped_width, $cropped_height); 
    // 缩放
    imagecopyresampled($target_image, $cropped_image, 0, 0, 0, 0, $target_width, $target_height, $cropped_width, $cropped_height);

    header('Content-Type: image/jpeg');
    imagejpeg($target_image);
    imagedestroy($source_image);
    imagedestroy($target_image);
    imagedestroy($cropped_image);
}
//该片段来自于http://outofmemory.cn