Rendering fonts with Freetype and OpenGL - opengl

Question

I have problem freetype and OpenGL. I need just draw all loaded symbols on single texture. Here's:
FT_Init_FreeType(&lib);
FT_New_Face(lib, "C:\\verdana.ttf", 0, &face);
FT_Set_Pixel_Sizes(face, 0, size);
auto ww = 256 * size;
auto hh = size;
std::vector<unsigned char> buffer(ww * hh, 0);
int off = 0;
for (int c = 0; c < 256; c++)
{
FT_UInt GlyphIndex;
GlyphIndex = FT_Get_Char_Index(face, c);
FT_Load_Char(face, GlyphIndex, FT_LOAD_RENDER);
FT_Bitmap bmp = face->glyph->bitmap;
int advance = (face->glyph->advance.x >> 6);
int bW = bmp.width;
int bH = bmp.rows;
for (int h = 0; h < bH; ++h) {
for (int w = 0; w < bW; ++w) {
buffer[h * bW + off + w] = bmp.buffer[w + bW * h];
}
}
off += advance;
}
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, ww, hh, 0, GL_ALPHA, GL_UNSIGNED_BYTE, &buffer[0]);
I tried many ways to do this. But all I get is absolutely black texture...
What's wrong with my code?

Answer 1

I think the problem is that some values between 0-255 is not visible or drawable character and that's why you get nothing.
you should check for GlyphIndex:
GlyphIndex = FT_Get_Char_Index(face, c);
if (!GlyphIndex) continue;
then you can expect freetype to draw the rest of characters for you.

Answer 2

hallelujah, I got solution!
This should look like this:
for (int c = 0; c < 256; c++)
{
FT_UInt GlyphIndex;
GlyphIndex = FT_Get_Char_Index(face, c);
FT_Load_Char(face, GlyphIndex, FT_LOAD_RENDER);
FT_Bitmap bmp = face->glyph->bitmap;
int advance = (face->glyph->advance.x >> 6);
int bW = bmp.width;
int bH = bmp.rows;
for (int h = 0; h < bH; ++h) {
for (int w = 0; w < bW; ++w) {
buffer[h * ww + off + w] = bmp.buffer[w + bW * h];
}
}
off += advance;
}
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_R8, ww, hh, 0, GL_RED, GL_UNSIGNED_BYTE, &buffer[0]);