php - 在php中以百分比计算图像大小

Question

我有一段代码在上传照片的右下角添加水印。但是，水印不会像我想要的那样根据上传的照片改变大小。我想按百分比计算它的比例，所以水印总是上传照片的 10% 并放在右下角。如何才能做到这一点？

这是我的代码：

// Load the stamp and the photo to apply the watermark to
$stamp = imagecreatefromgif('../images/watermark.gif');

$marge_right = 5;
$marge_bottom = 5;
$sx = imagesx($stamp);
$sy = imagesy($stamp);

$im = imagecreatefromjpeg($file_tmp)
imagecopymerge($im, $stamp, imagesx($im) - $sx - $marge_right,
 imagesy($im) - $sy - $marge_bottom, 0, 0, imagesx($stamp), imagesy($stamp), 30);

Answer 1

对于 PHP5.5 之前的版本，但至少是 PHP 4，您可以像这样缩放图像：

function scale($image, $percentage)
{
    $w = imagesx($image) * $percentage;
    $h = imagesy($image) * $percentage;
    $newimage = imagecreatetruecolor($w, $h);
    imagecopyresized($newimage, $image, 0, 0, 0, 0, $w, $h,
                                                   imagesx($image), imagesy($image));
    return $newimage;
}

$scaledImage = scale($originalImage, 0.5); // scale by 50%

Answer 2

如果您有 PHP 5.5+，请这样做：

// Load the stamp and the photo to apply the watermark to
$stamp = imagecreatefromgif('../images/watermark.gif');
$im = imagecreatefromjpeg($file_tmp);

$marge_right = 5;
$marge_bottom = 5;

$percent = 10;
$factor = 1 - ($percent/100); 

$stampscaled = imagescale ($stamp, $factor * $imagesx($im));

$sx = imagesx($stampscaled);
$sy = imagesy($stampscaled);

imagecopymerge($im, $stamp, imagesx($im) - $marge_right - $sx,
 imagesy($im) - $marge_bottom - $sy, 0, 0, $factor * imagesx($im), $factor * imagesy($im), 30);

注意：这适用于大小大致为矩形的源图像。对于极端的纵横比，您可能需要使用更复杂的缩放。