PHP Imagick：将图像对象复制到另一个图像对象，但分辨率更高

Why doesn't this work?

var_dump($Obj_old_image->getImageResolution());
//array(2) { ["x"]=> float(72) ["y"]=> float(72) } 

$Obj_new_image->setResolution(200, 200);

var_dump($Obj_new_image->getImageResolution());
//array(2) { ["x"]=> float(200) ["y"]=> float(200) } 

$Obj_new_image->setImage($Obj_old_image);

$Obj_new_image->setImageFormat("png");
header("Content-Type: image/png");
echo $Obj_new_image;

It returns the same resolution.

This is supposed to resize an SVG image without losing quality.

I have no idea what $Obj_old_image is or what it is doing based on your posted code. However the following code will work with PHP and the standard GD lib installed:

// image to be scaled
$rawImgPath = './test.jpg';

// new image size (guessing you know the new size)
$newImgSize['w'] = 200;
$newImgSize['h'] = 200;

// the steps to create the new scaled image
$rawImg = imagecreatefromjpeg($rawImgPath);
$newImg = imagecreatetruecolor($newImgSize['w'], $newImgSize['h']);

// need to know the current width and height of the source image
list($rawImgSize['w'], $rawImgSize['h']) = getimagesize($rawImgPath);

// resize the iamge
imagecopyresampled($newImg,$rawImg, 0,0,0,0,
    $newImgSize['w'],$newImgSize['h'],$rawImgSize['w'],$rawImgSize['h']);

// no longer need the original
imagedestroy($rawImg);

// display scaled image
header('Content-Type: image/png');
imagepng($newImg);

// no longer need the scaled image
imagedestroy($newImg);

And this code should work and give better results, but does not for me. Basically, imagescale() is newish code and is not well document on the PHP site.

// image to be scaled
$rawImgPath = './test.jpg';

// new image size (guessing you know the new size)
$newImgSize['w'] = 200;
$newImgSize['h'] = 200;

// the steps to create the new scaled image
$rawImg = imagecreatefromjpeg($rawImgPath);
$newImg = imagescale($rawImg, $newImgSize['w'], $newImgSize['h'],
    IMG_BICUBIC_FIXED);

// no longer need the original
imagedestroy($rawImg);

// display scaled image
header('Content-Type: image/png');
imagepng($newImg);

// no longer need the scaled image
imagedestroy($newImg);

Just use PHP's native clone keyword to duplicate Imagick instances.

$smallImg = new Imagick('small.png')
$newImg = clone $smallImg;

$newImg->resizeImage(200, 200, Imagick::FILTER_LANCZOS, 1, true);

$newImg->setImageFormat("png");
header("Content-Type: image/png");
echo $newImg;

The bestfit argument to resizeImage (last boolean) is required to scale up. Without that, Imagick will only scale down, leaving smaller images unchanged.

A comment on the Imagick::resizeImage docs compares speeds for the various resize filters. I've had good results with Lanczos.