[ubuntu-art] PHP/MySQL tasks on the art.ubuntu.com website

[Thomas Wood]

At the moment thumbnails are scales to a horizontal width of 96px, so 
the width is fixed, but the height is scaled. The easiest ImageMagick 
command for this is `mogrify -scale 96 filename.png`, but we also have 
some GD code in the screenshots the does appropriate scaling.

The GD library includes some useful methods for manipulating images, as 
well as determining height, width and image type. The getimagesize() 
function not only returns the image size, but also the image type. The 
interesting thing about this function is that unlike other GD functions, 
it takes a filename as an argument, so it doesn't require the whole 
image to be loaded into memory.

The disadvantage of using GD to scale images is that it requires the 
image to be loaded into memory, which can cause PHP try and allocate 
more memory than the max value set in the PHP configuration. I would 
suggest we use GD to determine information about the images, such as 
type and size, and then use Imagemagick to scale them.

I am hoping we can add support for SVG images too, but this would 
probably require having librsvg installed on the server. librsvg 
includes a command line application to export SVG files to raster.

-Thomas


Matthew Nuzum wrote:
> On 9/6/05, Christian Bjälevik <nafallo at magicalforest.se> wrote:
> 
>>tis 2005-09-06 klockan 11:41 +0100 skrev Henrik Nilsen Omma:
>>
>>>Hi,
>>>
>>
>>[snip]
>>
>>>* Automatically generated thumbnails (on upload). From backgrounds,
>>>screenshots, etc. we could get automatically generated 96x72px
>>>thumbnails with Imagemagik or GD, saving the uploader from making them.
>>
>>Rather than having 96x72px we should have something that will generate
>>the thumbnail based on aspect. Otherwise we will have trouble later when
>>people start uploading in 16:9 (16:10?). Not everything is 4:3
>>anymore ;-).
>>
>>[snip]
> 
> 
> Here are some useful ImageMagick commands i use in some of my PHP programs:
> find the width and height of an image:
> "identify -ping -format '%w~%h' $imagename"
> Returns width and height in pixels separated by a tilde (~). From PHP
> you can then split the output on the tilde and get the width and
> height for use in scaling the image.
> 
> Resize an image:
> "mogrify -geometry $width"."x".$height $file"
> For example, mogrify -geometry 640x480 splash.png (note there are no
> spaces in the 640x480)
> 
> Composite two images. This is useful in the case where your thumbnails
> should keep the aspect ratio of the original image, but you want your
> thumbnail to always be a certain size. You can have a little php code
> that will use identify to get the dimensions, then do some math to
> keep the aspect ratio the same but find the width and height so that
> neither are larger than 96 px. Use the mogrify command to scale the
> image. Then, you can use the following command to composite the scaled
> image onto a clear (or white) 96x96 image so that your HTML can assume
> a constant thumbnail size while avoiding image distortion:
> "composite $image1 $image2 $output"
> 
> So, here is some psuedo code that resembles PHP that will grab an
> uploaded image and create two thumbnails that are no larger than 96x96
> and 200x200.
> 
> // preset the values for $image1_temp, $image2_temp, $white96x96 and
> $white200x200
> 
> // $image_temp is the original image we'll be resizing
> $dimensions = `/usr/bin/identify -ping -format '%w~%h' $image_temp`;
> list($width, $height) = explode("~", $dimensions);
> 
> // find the dimensions for the new thumbnails
> // $thumb1 will be max 96x96, $thumb2 will be max 200x200
> if ($width > $height) {
>     $width1 = 96;
>     $width2 = 200;
>     $height1 = round( (96*$height)/$width);
>     $height2 = round( (200*$height)/$width);
> }elseif($height > $width) {
>     $height1 = 96;
>     $height2 = 200;
>     $width1 = round( (96*$width)/$height);
>     $width2 = round( (200*$width)/$height);
> } else {
>     $height1 = $width1 = 96;
>     $height2 = $width2 = 200;
> }
> 
> // create temporary thumbnails with proportial dimensions
> copy($image_temp, $thumb1_temp);
> copy($image_temp, $thumb2_temp);
> $ok = `/usr/bin/mogrify -geometry $width1"."x".$height1 $thumb1_temp";
> $ok = `/usr/bin/mogrify -geometry $width2"."x".$height2 $thumb2_temp";
> 
> // create the final thumbnails
> $ok = `/usr/bin/composite $thumb1_temp $white96x96 $thumb1`;
> $ok = `/usr/bin/composite $thumb2_temp $white200x200 $thumb2`;
>