如何将.png文件转换为.bmp文件？

I need to convert a .png file to .bmp; I'm using the outcome in printer_draw_bmp() to print out a barcode.

GD can generate WBMP, but as far as I can tell that's not the same as .bmp. How can I do this conversion? Or is there another way to print a .png directly?

There is a opensource project on Github that allows reading and saving of BMP files (and other file formats) in PHP.

The project is called PHP Image Magician.

AFAIK, GD doesn't support bmp format. But you can use ImageMagick to save file in bmp format:

$im = new Imagick('image.png');
$im->writeImage('image.bmp');

Or if you want to output image to http response:

$im = new Imagick('image.png');
$im->setImageFormat('bmp');
echo $im;