如何将所有图片转换为jpg格式？

Question

我有脚本：

<?php

include('db.php');
session_start();
$session_id = '1'; // User session id
$path = "uploads/";

$valid_formats = array("jpg", "png", "gif", "bmp", "jpeg");
if (isset($_POST) and $_SERVER['REQUEST_METHOD'] == "POST") {
    $name = $_FILES['photoimg']['name'];
    $size = $_FILES['photoimg']['size'];
    if (strlen($name)) {
        list($txt, $ext) = explode(".", $name);
        if (in_array($ext, $valid_formats)) {
            if ($size < (1024 * 1024)) { // Image size max 1 MB
                $actual_image_name = time() . $session_id . "." . $ext;
                $tmp = $_FILES['photoimg']['tmp_name'];
                if (move_uploaded_file($tmp, $path . $actual_image_name)) {
                    mysql_query("UPDATE users SET profile_image='$actual_image_name' WHERE uid='$session_id'");
                    echo "<img src='uploads/" . $actual_image_name . "' class='preview'>";
                } else {
                    echo "failed";
                }
            } else {
                echo "Image file size max 1 MB";
            }
        } else {
            echo "Invalid file format..";
        }
    } else {
        echo "Please select image..!";
    }
    exit;
}

?>

有没有可能将所有图像(png，gif等)转换为100%质量的jpg？如果是，是如何实现的？我想允许上传png和gif，但此脚本应转换此文件为jpg。PHP能做到这一点吗？

Answer 1

试试这段代码：originalImage是...的路径原始图像..。outputImage已经足够自我解释了。

function convertImage($originalImage, $outputImage, $quality)
{
    // jpg, png, gif or bmp?
    $exploded = explode('.',$originalImage);
    $ext = $exploded[count($exploded) - 1]; 

    if (preg_match('/jpg|jpeg/i',$ext))
        $imageTmp=imagecreatefromjpeg($originalImage);
    else if (preg_match('/png/i',$ext))
        $imageTmp=imagecreatefrompng($originalImage);
    else if (preg_match('/gif/i',$ext))
        $imageTmp=imagecreatefromgif($originalImage);
    else if (preg_match('/bmp/i',$ext))
        $imageTmp=imagecreatefrombmp($originalImage);
    else
        return 0;

    // quality is a value from 0 (worst) to 100 (best)
    imagejpeg($imageTmp, $outputImage, $quality);
    imagedestroy($imageTmp);

    return 1;
}

Answer 2

尝试使用Imagick setImageFormat，对我来说，它提供了最好的图像质量

http://php.net/manual/en/imagick.setimageformat.php

$im = new imagick($image);

// convert to png
$im->setImageFormat('png');

//write image on server
$im->writeImage($image .".png");
$im->clear();
$im->destroy(); 

Answer 3

Davide Berra的答案很好，所以我对文件类型检测做了一些改进，使用exif_imagetype()而不是依赖于文件扩展名：

/**
*   Auxiliar function to convert images to JPG
*/
function convertImage($originalImage, $outputImage, $quality) {

    switch (exif_imagetype($originalImage)) {
        case IMAGETYPE_PNG:
            $imageTmp=imagecreatefrompng($originalImage);
            break;
        case IMAGETYPE_JPEG:
            $imageTmp=imagecreatefromjpeg($originalImage);
            break;
        case IMAGETYPE_GIF:
            $imageTmp=imagecreatefromgif($originalImage);
            break;
        case IMAGETYPE_BMP:
            $imageTmp=imagecreatefrombmp($originalImage);
            break;
        // Defaults to JPG
        default:
            $imageTmp=imagecreatefromjpeg($originalImage);
            break;
    }

    // quality is a value from 0 (worst) to 100 (best)
    imagejpeg($imageTmp, $outputImage, $quality);
    imagedestroy($imageTmp);

    return 1;
}

您必须启用php_exif扩展才能使用此扩展。