func LoadBitmap(img, config io.Reader, scale int) (*Font, error) {
	pix, _, err := image.Decode(img)
	if err != nil {
		return nil, err
	}
	rgba := toRGBA(pix, scale)
	var fc FontConfig
	err = fc.Load(config)
	if err != nil {
		return nil, err
	}
	fc.Glyphs.Scale(scale)
	return loadFont(rgba, &fc)
}
LoadBitmap loads a bitmap (raster) font from the given
sprite sheet and config files. It is optionally scaled by
the given scale factor.

A scale factor of 1 retains the original size. A factor of 2 doubles the
font size, etc. A scale factor of 0 is not valid and will default to 1.

Supported image formats are 32-bit RGBA as PNG, JPEG and GIF.
package gltext
import (
	"image"
	_ "image/gif"
	_ "image/jpeg"
	_ "image/png"
	"io"
)