void Font::CalculateAdvances(ImageBuffer &image)
{
// Get the format and size of the surface.
int width = image.Width() / GLYPHS;
height = image.Height();
unsigned mask = 0xFF000000;
unsigned half = 0xC0000000;
int pitch = image.Width();
// advance[previous * GLYPHS + next] is the x advance for each glyph pair.
// There is no advance if the previous value is 0, i.e. we are at the very
// start of a string.
memset(advance, 0, GLYPHS * sizeof(advance[0]));
for(int previous = 1; previous < GLYPHS; ++previous)
for(int next = 0; next < GLYPHS; ++next)
{
int maxD = 0;
int glyphWidth = 0;
uint32_t *begin = image.Pixels();
for(int y = 0; y < height; ++y)
{
// Find the last non-empty pixel in the previous glyph.
uint32_t *pend = begin + previous * width;
uint32_t *pit = pend + width;
while(pit != pend && (*--pit & mask) < half) {}
int distance = (pit - pend) + 1;
glyphWidth = max(distance, glyphWidth);
// Special case: if "next" is zero (i.e. end of line of text),
// calculate the full width of this character. Otherwise:
if(next)
{
// Find the first non-empty pixel in this glyph.
uint32_t *nit = begin + next * width;
uint32_t *nend = nit + width;
while(nit != nend && (*nit++ & mask) < half) {}
// How far apart do you want these glyphs drawn? If drawn at
// an advance of "width", there would be:
// pend + width - pit <- pixels after the previous glyph.
// nit - (nend - width) <- pixels before the next glyph.
// So for zero kerning distance, you would want:
distance += 1 - (nit - (nend - width));
}
maxD = max(maxD, distance);
// Update the pointer to point to the beginning of the next row.
begin += pitch;
}
// This is a fudge factor to avoid over-kerning, especially for the
// underscore and for glyph combinations like AV.
advance[previous * GLYPHS + next] = max(maxD, glyphWidth - 4) / 2;
}
// Set the space size based on the character width.
width /= 2;
height /= 2;
space = (width + 3) / 6 + 1;
}
void Font::Load(const string &imagePath)
{
// Load the texture.
ImageBuffer image;
if(!image.Read(imagePath))
return;
LoadTexture(image);
CalculateAdvances(image);
SetUpShader(image.Width() / GLYPHS, image.Height());
}
void Font::LoadTexture(ImageBuffer &image)
{
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, image.Width(), image.Height(), 0,
GL_BGRA, GL_UNSIGNED_BYTE, image.Pixels());
}
void Font::Load(const string &imagePath)
{
// Load the texture.
ImageBuffer *image = ImageBuffer::Read(imagePath);
if(!image)
return;
LoadTexture(image);
CalculateAdvances(image);
SetUpShader(image->Width() / GLYPHS, image->Height());
delete image;
}