WBMP output doesn't work

[AaronV]

Hello, I'm having a probelm output wbmp images. Something seems to keep
going wrong with the encoding, because I start with a good jpeg and get
a nonworking wbmp on the other end.

here is my code:

$image_p = imagecreatetruecolor($new_width, $new_height);
$image = imagecreatefromjpeg($filename);
imagecopyresampled($image_p, $image, 0, 0, 0, 0, $new_width,
$new_height, $width, $height);

// Output new image
imagewbmp($image_p, "..path..");
Replacing the imagewbmp with imagejpeg will output a valid jpeg file,
or I can output a valid PNG as well. But outputing a wbmp never works,
I get a busted image. Anyone know what's going on here? Am I missing
some color conversion step?

[AaronV]

I checked the gd_info() and wbmp support is enabled, btw.

[Andy Hassall]

On 5 Aug 2005 18:25:07 -0700, "AaronV" <aa**************@gmail.com> wrote:

Hello, I'm having a probelm output wbmp images. Something seems to keep
going wrong with the encoding, because I start with a good jpeg and get
a nonworking wbmp on the other end.

here is my code:

$image_p = imagecreatetruecolor($new_width, $new_height);
$image = imagecreatefromjpeg($filename);
imagecopyresampled($image_p, $image, 0, 0, 0, 0, $new_width,
$new_height, $width, $height);

// Output new image
imagewbmp($image_p, "..path..");
Replacing the imagewbmp with imagejpeg will output a valid jpeg file,
or I can output a valid PNG as well. But outputing a wbmp never works,
I get a busted image. Anyone know what's going on here? Am I missing
some color conversion step?

OK, in what way is it busted?

Zero length file? Or actually producing a corrupted file in some way?

Anything obvious in the file itself like error messages? (Presumably not since
it's using the path argument in the GD call, but worth a quick look).

--
Andy Hassall / <an**@andyh.co.uk> / <http://www.andyh.co.uk>
<http://www.andyhsoftware.co.uk/space> Space: disk usage analysis tool

[Janwillem Borleffs]

AaronV wrote:

Replacing the imagewbmp with imagejpeg will output a valid jpeg file,
or I can output a valid PNG as well. But outputing a wbmp never works,
I get a busted image. Anyone know what's going on here? Am I missing
some color conversion step?

The problem is that WBMP can only be created from images which contain black
and white only.

The imagetruecolortopalette() function seems to be able to reduce the color
depth, but the result will still be insufficient to create a WBMP image,
because it will not consist of just black and white.

One solution is to map the pixels to either black or white manually. You
will need to to this after you have resampled the image and before you call
imagewbmp().

The following code produced reasonable results with the images I have tested
it with:

for ($y = 0; $y < $new_height; $y++) {
for ($x = 0; $x < $new_width; $x++) {
$colors = imagecolorsforindex(
$image_p,
imagecolorat($image_p, $x, $y)
);

if ($colors['red'] > 180) {
$color = imagecolorallocate($image_p, 255, 255, 255);
} else {
$color = imagecolorallocate($image_p, 0, 0, 0);
}
imagesetpixel($image_p, $x, $y, $color);
}
}

As I said, you should insert this code just after you have called
imagecopyresampled() and before calling imagewbmp().
HTH;
JW