Thumbnails - Halving width but doubling height?

[Jeigh]

Hello, I've been searching for a tutorial to create thumbnails for a while and finally found one that works for me. It's doing everything it's suppose to except one thing.

I created a test image 600px wide, 700px high, so to get 300px width it would need to half that, as well as the 700px height. It's resizing the width to half the size (300px) except instead of halfing the height to 350px, it doubles it to 1400px, which obviously causes the image to come out very wrong.

Here's the code I'm using:

function createThumbnail($imageDirectory, $imageName, $thumbDirectory, $thumbWidth)
{
$srcImg = imagecreatefromjpeg("$imageDirectory/$imageName");
$origWidth = imagesx($srcImg);
$origHeight = imagesy($srcImg);
 
$ratio = $origWidth / $thumbWidth;
$thumbHeight = $origHeight * $ratio;
 
$thumbImg = imagecreate($thumbWidth, $thumbHeight);
imagecopyresized($thumbImg, $srcImg, 0, 0, 0, 0, $thumbWidth, $thumbHeight, imagesx($thumbImg), imagesy($thumbImg));
 
imagejpeg($thumbImg, "$thumbDirectory/$imageName");
}
 
createThumbnail("uploads/examples", "$newname", "uploads/examples/thumbnails", 300);
 

Thanks,
Jeigh.

[jx2]

change line 7
[php]
ratio = $thumbWidth / $origWidth ;
[/php]

regards
jx2

[Atli]

Hi.

At line 8, you should divide, not multiply.

[jx2]

Hi.

At line 8, you should divide, not multiply.

LOL i think you're confusing him
yeah
it can be your way

regards
jx2

[Atli]

LOL i think you're confusing him
yeah
it can be your way

regards
jx2

Well, there are two ways I would consider using for this.

The first one. I've used a number of times.

$ratio = $originalHeight / $originalWidth;
$thumbHeight = $thumbWidth * $ratio;
 

The second one. A little limited but works in this case.

$ratio = $originalWidth / $thumbWidth;
$thumbHeight = $originalHeight / $ratio;
 

I'ts like Jeigh was using the second one but mixed up the second line. Has probbly happend to all of us at some point.

[Jeigh]

Thanks for that guys, it worked but it seems to crop the image instead of resizing it, am I using the wrong sort of script or can this be modified to do that?

[jx2]

Thanks for that guys, it worked but it seems to crop the image instead of resizing it, am I using the wrong sort of script or can this be modified to do that?

look here

you need two more parameters in line 11 for sorce height and width

regards
jx2

[Atli]

look here

you need two more parameters in line 11 for sorce height and width

regards
jx2

This one is pretty much the same imagecopyresampled(), except this one not only resizes the image, it also resamples it, so it gives you better quality.

[jx2]

This one is pretty much the same imagecopyresampled(), except this one not only resizes the image, it also resamples it, so it gives you better quality.

thx Atli
nice job i didnt know that one ;-)

regards
jx2

[Jeigh]

I had a look at the links you gave me and now I'm using:

function createThumbnail($imageDirectory, $imageName, $thumbDirectory, $thumbWidth)
{
$srcImg = imagecreatefromjpeg("$imageDirectory/$imageName");
$origWidth = imagesx($srcImg);
$origHeight = imagesy($srcImg);
 
list($width, $height) = getimagesize($newname);
 
$ratio = $origWidth / $thumbWidth;
$thumbHeight = $origHeight / $ratio;
 
$thumbImg_p = imagecreatetruecolor($thumbWidth, $thumbHeight);
 
imagecopyresampled($thumbImg_p, $srcImg, 0, 0, 0, 0, $thumbWidth, $thumbHeight, imagesx($thumbImg), imagesy($thumbImg));
 
imagejpeg($thumbImg_p, "$thumbDirectory/$imageName");
}
 
createThumbnail("uploads/examples", "$newname", "uploads/examples/thumbnails", 300);  
 

But I'm still getting the same result, the correct size but it's cropped instead of resized. Obviously I'm missing somthing I just dont know what :P

(This is the first time I've used anything with GD)

[Atli]

The last two parameters of the imagecopyresampled() function, you use in line 14, are supposed to be the size of the original image, not the thumbnail.

Try this:

imagecopyresampled($thumbImg_p, $srcImg, 0, 0, 0, 0, $thumbWidth, $thumbHeight, $origWidth, $origHeight);
 

[Jeigh]

Ah, thanks a lot Atli. Works great now :D

Just trying to get it to work with .png and .gif as well as just jpeg using this:

 
function createThumbnail($imageDirectory, $imageName, $thumbDirectory, $thumbWidth)
{
 
switch ($ext) {
case ".jpeg":
$srcImg = imagecreatefromjpeg("$imageDirectory/$imageName");
    break;
case ".png":
$srcImg = imagecreatefrompng("$imageDirectory/$imageName");
    break;
case ".gif":
$srcImg = imagecreatefromgif("$imageDirectory/$imageName");
    break;
}
 
$origWidth = imagesx($srcImg);
$origHeight = imagesy($srcImg);
 
list($width, $height) = getimagesize($newname);
 
$ratio = $origWidth / $thumbWidth;
$thumbHeight = $origHeight / $ratio;
 
$thumbImg_p = imagecreatetruecolor($thumbWidth, $thumbHeight);
$thumbImg = imagecreate($thumbWidth, $thumbHeight);
/*imagecopyresized($thumbImg, $srcImg, 0, 0, 0, 0, $thumbWidth, $thumbHeight, imagesx($thumbImg), imagesy($thumbImg));*/
 
imagecopyresampled($thumbImg_p, $srcImg, 0, 0, 0, 0, $thumbWidth, $thumbHeight, $origWidth, $origHeight);
 
switch ($ext) {
case ".jpeg":
imagejpeg($thumbImg_p, "$thumbDirectory/$imageName");
    break;
case ".png":
imagepng($thumbImg_p, "$thumbDirectory/$imageName");
    break;
case ".gif":
imagegif($thumbImg_p, "$thumbDirectory/$imageName");
    break;
}
 
 
}
 
createThumbnail("uploads/examples", "$newname", "uploads/examples/thumbnails", 300);  
 

Which brings up an error for just about every function I was using, any clues?

[Atli]

You are using a variable called $ext in the two switch statements that has no value. I would guess that's the problem.

[Jeigh]

Sorry, forgot to mention, $ext is defined earlier in the script, which is just the extension of the file:

 $ext = strrchr($_FILES['uploaded_image']['name'], "."); 
        if ($ext != ".gif" AND $ext != ".jpg" AND $ext != ".jpeg" AND $ext != ".bmp" AND $ext != ".GIF" AND $ext != ".JPG" AND $ext != ".JPEG" AND $ext != ".BMP" AND $ext != ".png") { 
            $error = "your file was an unacceptable type.<br />";
 

[jx2]

Sorry, forgot to mention, $ext is defined earlier in the script, which is just the extension of the file:

 $ext = strrchr($_FILES['uploaded_image']['name'], "."); 
        if ($ext != ".gif" AND $ext != ".jpg" AND $ext != ".jpeg" AND $ext != ".bmp" AND $ext != ".GIF" AND $ext != ".JPG" AND $ext != ".JPEG" AND $ext != ".BMP" AND $ext != ".png") { 
            $error = "your file was an unacceptable type.<br />";
 

is it a code writen whitin the function or $ext is global variable?

if this is code writen outside this function you need to make sure $ext exist in a function

[php]global $ext;[/php]

line 22[php]$thumbImg = imagecreate($thumbWidth, $thumbHeight);[/php]
you never uuse this variable what this is for?

i strongly recomend you try to write this function on your own (its not very difficukt!!) so you can know how it works

regards
jx2

[Atli]

Sorry, forgot to mention, $ext is defined earlier in the script, which is just the extension of the file:

 $ext = strrchr($_FILES['uploaded_image']['name'], "."); 
        if ($ext != ".gif" AND $ext != ".jpg" AND $ext != ".jpeg" AND $ext != ".bmp" AND $ext != ".GIF" AND $ext != ".JPG" AND $ext != ".JPEG" AND $ext != ".BMP" AND $ext != ".png") { 
            $error = "your file was an unacceptable type.<br />";
 

If this variable is created outside the function it is likely that it will not work inside your function. You must either make it global, as Jx2 suggessted, or somehow import it into the function.
Personally I would pass it into the function as a parameter.

[Jeigh]

Thanks guys, using global fixed it :)