setting imagecreatetruecolor() to have transparency as default

[Chamomile]

Does anyone know if its possible to set imagecreatetruecolor() to initialise
with transparency
rather than black?
Maybe a cunning work-around?

[Kimmo Laine]

"Chamomile" <ne********@chamomile.co.uk> wrote in message
news:ir******************************@bt.com...

Does anyone know if its possible to set imagecreatetruecolor() to
initialise
with transparency
rather than black?
Maybe a cunning work-around?

It's mentioned in the user comments in php.net manual page:
http://fi.php.net/manual/en/function...olor.php#54025

// Creates a transparent image rather than the default black image
function imageCreateTransparent($x, $y) {
$imageOut = imagecreate($x, $y);
$colourBlack = imagecolorallocate($imageOut, 0, 0, 0);
imagecolortransparent($imageOut, $colourBlack);
return $imageOut;
}

HTH

--
"ohjelmoija on organismi joka muuttaa kofeiinia koodiksi" -lpk
sp**@outolempi.net | Gedoon-S @ IRCnet | rot13(xv***@bhgbyrzcv.arg)

[Chamomile]

>

It's mentioned in the user comments in php.net manual page:
http://fi.php.net/manual/en/function...olor.php#54025

// Creates a transparent image rather than the default black image
function imageCreateTransparent($x, $y) {
$imageOut = imagecreate($x, $y);
$colourBlack = imagecolorallocate($imageOut, 0, 0, 0);
imagecolortransparent($imageOut, $colourBlack);
return $imageOut;
}

HTH

--
"ohjelmoija on organismi joka muuttaa kofeiinia koodiksi" -lpk
sp**@outolempi.net | Gedoon-S @ IRCnet | rot13(xv***@bhgbyrzcv.arg)

Yes, thanks - I came accross that.
The problem is, it only makes a non-truecolor image which is no good for my
purposes
as I am downsampling with imagecopyresample() in order to get 'aliased'
curve fills at small sizes.
- downsampling an image made using imagecreate() gives jagged curves,
whereas downsampling using imagecreatetruecolor() gives good smoothing.
Unfotunately it seems once an image has ever been truecolor - even if you
theoretically set it back to paletted colors
(as far as I can see with experimentation) you cannot re-set the
transparency of the 'black' areas.

It seems to be a choice between smoothed curves or transparency - not both!

[NC]

Chamomile wrote:

Does anyone know if its possible to set imagecreatetruecolor()
to initialise with transparency rather than black?

My first instinctive reaction would be to say no. Transparency is
supported in GIF and PNG formats, but not in JPEG. So when you attempt
to create an image that doesn't yet have a format associated with it,
you shouldn't expect it to contain features specific to a format you
have not yet defined...

Cheers,
NC

[Kimmo Laine]

"Chamomile" <ne********@chamomile.co.uk> wrote in message
news:OJ********************@bt.com...

Yes, thanks - I came accross that.
The problem is, it only makes a non-truecolor image which is no good for
my
purposes
as I am downsampling with imagecopyresample() in order to get 'aliased'
curve fills at small sizes.
- downsampling an image made using imagecreate() gives jagged curves,
whereas downsampling using imagecreatetruecolor() gives good smoothing.
Unfotunately it seems once an image has ever been truecolor - even if you
theoretically set it back to paletted colors
(as far as I can see with experimentation) you cannot re-set the
transparency of the 'black' areas.

It seems to be a choice between smoothed curves or transparency - not
both!

A slight modification to the original sample seems to answer the question.

<?php

header('Content-type: image/png');
$imageOut = imagecreate(100, 100);
$colourBlack = imagecolorallocatealpha($imageOut, 0, 0, 0, 127);
imagepng($imageOut);

?>

This worked for me so that when I saved the image and opened it in photoshop
it really was transparent. The solution apparently is that the first color
you allocate defines the background of the image. Now if you use
imagecolorallocatealpha and give 127 as the alpha channel, you'll get a
truecolor image with completely transparent bg.

HTH, again ;)

--
"ohjelmoija on organismi joka muuttaa kofeiinia koodiksi" -lpk
sp**@outolempi.net | Gedoon-S @ IRCnet | rot13(xv***@bhgbyrzcv.arg)