Image resize - no loss of dpi

[AndieB]

Hi all!

 

I have used the below script to resize images, but every picture uploaded seems to loss quality and I can not figure out why?

Perhaps anyone who reads this can help me out!

 

	// CHECK WHAT FORMAT THE PICTURE IS, LANDSCAPE OR PORTRAIT
$fileSize = getimagesize($uploaddir . $tmpnewfilename);
$new_file_width = $fileSize['width'];
$new_file_height = $fileSize['height'];

if ($new_file_height > $new_file_width) {
	$new_file_new_width = 427;
	$new_file_new_height = 307;

	$destimg = ImageCreateTrueColor( $new_file_new_width, $new_file_new_height ) or die( "Problem In Creating image" );
	$srcimg = ImageCreateFromJPEG( $uploaddir.$tmpnewfilename ) or die( "Problem In opening Source Image" );

	ImageCopyResampled( $destimg, $srcimg, 0, 0, 0, 0, $new_file_new_width, $new_file_new_height,ImageSX($srcimg),ImageSY($srcimg)) or die("Problem In resizing");
	ImageJPEG($destimg,$uploaddir.$newfilename) or die("Problem In saving");
	unlink($uploaddir . $tmpnewfilename);
} else {
	$new_file_new_width = 640;
	$new_file_new_height = 427;

	$destimg=ImageCreateTrueColor($new_file_new_width,$new_file_new_height) or die("Problem In Creating image");
	$srcimg=ImageCreateFromJPEG($uploaddir.$tmpnewfilename) or die("Problem In opening Source Image");

	ImageCopyResampled($destimg,$srcimg,0,0,0,0,$new_file_new_width,$new_file_new_height,ImageSX($srcimg),ImageSY($srcimg)) or die("Problem In resizing");
	ImageJPEG($destimg,$uploaddir.$newfilename) or die("Problem In saving");
	unlink($uploaddir . $tmpnewfilename);
}

 

Does the DPI (Dots Per Inch) change in the script above?

 

I would very much appreciate help!

 

Sincerely,

Andreas

[ToonMariner]

That's what images do - you are taking the same data and trying to place it all in a smaller (or larger) visual space.  this means that some interpolation will occur between pixels to try and replicate the colours.

 

The GD Library is not as sophisticated as graphic apps such as photoshop - they have sophistcaed algorithms and can far better utilise vector based algorithms to maintain the 'quality' of an image.

[AndieB]

So, I understand from your feedback that there are no hints or tips regarding maintaining better quality?

 

Thanks for you answer!

 

Sincerely,

Andreas