# OpenGL Freetype2 - Arial gives weird 'i' at 13 pixels

## Recommended Posts

Hey, I've been making my own wrapper around Freetype2 for OpenGL. However, I can't seem to easily fix this bug...it's bugging me ^^ Whenever I render the Arial font at 13 pixels height, the 'i' seems to be too high or w/e happens...this only happens when I use the Smooth feature of my wrapper, the Sharp feature works fine. Examples: 14 pixels smooth 13 pixels sharp 13 pixels smooth This is the code I use (without error handling):
                FT_Load_Char(face, character, FT_LOAD_RENDER);

FT_GlyphSlot &glyph = face->glyph;

FT_Glyph bbox_glyph;
FT_Get_Glyph(glyph, &bbox_glyph);

FT_BBox bbox;
FT_Glyph_Get_CBox(bbox_glyph, FT_GLYPH_BBOX_TRUNCATE, &bbox);

int width = pow2(glyph->bitmap.width);
int height = pow2(glyph->bitmap.rows);

if (width && height) // not a space character
{
GLuint texture = 0;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

GLubyte *buffer = NULL;
if (_sharpness == Sharpness::Smooth)
{
buffer = new GLubyte[height * width];
memset(buffer, 0x00, height * width);

for (int j = 0; j < glyph->bitmap.rows; j++)
{
memcpy(buffer + (j * width), glyph->bitmap.buffer + (j * glyph->bitmap.pitch), glyph->bitmap.pitch);
}

glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA8, width, height, 0, GL_ALPHA, GL_UNSIGNED_BYTE, buffer);
}
else if (_sharpness == Sharpness::Sharp)
{
buffer = new GLubyte[height * width * 2];
memset(buffer, 0x00, height * width * 2);

for (int j = 0; j < glyph->bitmap.rows; j++)
{
for (int i = 0; i < glyph->bitmap.pitch; i++)
{
buffer[(j * width * 2) + (i * 2)] = buffer[(j * width * 2) + (i * 2) + 1] = glyph->bitmap.buffer[(j * glyph->bitmap.pitch) + i];
}
}

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_LUMINANCE_ALPHA, GL_UNSIGNED_BYTE, buffer);
}
delete[] buffer;
}

// when drawing I use something like
glBindTexture(GL_TEXTURE_2D, character.texture);
glTexCoord2d(0,            0);            glVertex2f(0,           0);
glTexCoord2d(0,            (float) glyph->bitmap.rows / (float) height); glVertex2f(0,           glyph->bitmap.rows);
glTexCoord2d((float) glyph->bitmap.pitch / (float) width, (float) glyph->bitmap.rows / (float) height); glVertex2f(glyph->bitmap.pitch, glyph->bitmap.rows);
glTexCoord2d((float) glyph->bitmap.pitch / (float) width, 0);            glVertex2f(glyph->bitmap.pitch, 0);
glEnd();


What could possibly be wrong in the pixel copying (since I guess it's the pixel copying part, it only applies to Smooth not Sharp)? Thanks in advance.

##### Share on other sites
NeHe Productions has a very nice OpenGL text tutorial. I don't think it even relies on FreeType2. On the other hand I'm pretty sure it uses Windows-only functions. I followed it and never had any funny defects. Check it out if you haven't already. If you aren't using Windows, I apologize for making that assumption. I also don't understand why you calculate your width and height by using pow2(). Is pow2() your own function? I only know about pow().

##### Share on other sites
Hello fellow citizen! :)

I've written a font render engine once, only for learning how to do font rendering and for testing purposes. Didn't test it very well, so it might show the same problems. Anyway: I used the tutorials on the freetype 2 website itself and I found them quite easy to follow. It gave me results quickly.

My program ran on Linux using OpenGL and the tutorial I used can be found here:
http://www.freetype.org/freetype2/docs/tutorial/step1.html

You might want to compare your steps with the ones in this tutorial if you haven't seen it yet.

##### Share on other sites
@kittycat
I would like to use TTF fonts using FreeType2, and draw them in OpenGL. Don't want to be bound to windows only ;). And pow2 outputs the next following power of 2, which is needed for OGL textures (for older cards).

@TheFlyingDutchman

Hey, greetings! Nice weather eh xD

I followed the same tutorial ;). It works perfectly fine for almost anything, except this weird little bug. I think it has to do with the connection of FT2 with OpenGL...ie, the pixel copying. Not 100% sure, but it looks like it. Either that or the texture coordinates are wrong (which I don't think, since I had some rather random results...as if it was unused memory).

##### Share on other sites
You might want to try this, as I remember correctly I have seen several implementations having image corruption problems because the texture parameters weren't setup correctly:

glPixelStorei(GL_UNPACK_ALIGNMENT, 1);glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, texSize, texSize, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, data);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);

Especially the first line of code is important (the last four don't really matter for this I'd say). Hope this helps.

##### Share on other sites
Thanks! The first line made it work!

Awesome, it looks so sweet now :D

## Create an account

Register a new account

• ### Forum Statistics

• Total Topics
628316
• Total Posts
2982032
• ### Similar Content

• By mellinoe
Hi all,
First time poster here, although I've been reading posts here for quite a while. This place has been invaluable for learning graphics programming -- thanks for a great resource!
Right now, I'm working on a graphics abstraction layer for .NET which supports D3D11, Vulkan, and OpenGL at the moment. I have implemented most of my planned features already, and things are working well. Some remaining features that I am planning are Compute Shaders, and some flavor of read-write shader resources. At the moment, my shaders can just get simple read-only access to a uniform (or constant) buffer, a texture, or a sampler. Unfortunately, I'm having a tough time grasping the distinctions between all of the different kinds of read-write resources that are available. In D3D alone, there seem to be 5 or 6 different kinds of resources with similar but different characteristics. On top of that, I get the impression that some of them are more or less "obsoleted" by the newer kinds, and don't have much of a place in modern code. There seem to be a few pivots:
The data source/destination (buffer or texture) Read-write or read-only Structured or unstructured (?) Ordered vs unordered (?) These are just my observations based on a lot of MSDN and OpenGL doc reading. For my library, I'm not interested in exposing every possibility to the user -- just trying to find a good "middle-ground" that can be represented cleanly across API's which is good enough for common scenarios.
Can anyone give a sort of "overview" of the different options, and perhaps compare/contrast the concepts between Direct3D, OpenGL, and Vulkan? I'd also be very interested in hearing how other folks have abstracted these concepts in their libraries.
• By aejt
I recently started getting into graphics programming (2nd try, first try was many years ago) and I'm working on a 3d rendering engine which I hope to be able to make a 3D game with sooner or later. I have plenty of C++ experience, but not a lot when it comes to graphics, and while it's definitely going much better this time, I'm having trouble figuring out how assets are usually handled by engines.
I'm not having trouble with handling the GPU resources, but more so with how the resources should be defined and used in the system (materials, models, etc).
This is my plan now, I've implemented most of it except for the XML parts and factories and those are the ones I'm not sure of at all:
I have these classes:
For GPU resources:
Geometry: holds and manages everything needed to render a geometry: VAO, VBO, EBO. Texture: holds and manages a texture which is loaded into the GPU. Shader: holds and manages a shader which is loaded into the GPU. For assets relying on GPU resources:
Material: holds a shader resource, multiple texture resources, as well as uniform settings. Mesh: holds a geometry and a material. Model: holds multiple meshes, possibly in a tree structure to more easily support skinning later on? For handling GPU resources:
ResourceCache<T>: T can be any resource loaded into the GPU. It owns these resources and only hands out handles to them on request (currently string identifiers are used when requesting handles, but all resources are stored in a vector and each handle only contains resource's index in that vector) Resource<T>: The handles given out from ResourceCache. The handles are reference counted and to get the underlying resource you simply deference like with pointers (*handle).
And my plan is to define everything into these XML documents to abstract away files:
Resources.xml for ref-counted GPU resources (geometry, shaders, textures) Resources are assigned names/ids and resource files, and possibly some attributes (what vertex attributes does this geometry have? what vertex attributes does this shader expect? what uniforms does this shader use? and so on) Are reference counted using ResourceCache<T> Assets.xml for assets using the GPU resources (materials, meshes, models) Assets are not reference counted, but they hold handles to ref-counted resources. References the resources defined in Resources.xml by names/ids. The XMLs are loaded into some structure in memory which is then used for loading the resources/assets using factory classes:
Factory classes for resources:
For example, a texture factory could contain the texture definitions from the XML containing data about textures in the game, as well as a cache containing all loaded textures. This means it has mappings from each name/id to a file and when asked to load a texture with a name/id, it can look up its path and use a "BinaryLoader" to either load the file and create the resource directly, or asynchronously load the file's data into a queue which then can be read from later to create the resources synchronously in the GL context. These factories only return handles.
Factory classes for assets:
Much like for resources, these classes contain the definitions for the assets they can load. For example, with the definition the MaterialFactory will know which shader, textures and possibly uniform a certain material has, and with the help of TextureFactory and ShaderFactory, it can retrieve handles to the resources it needs (Shader + Textures), setup itself from XML data (uniform values), and return a created instance of requested material. These factories return actual instances, not handles (but the instances contain handles).

Is this a good or commonly used approach? Is this going to bite me in the ass later on? Are there other more preferable approaches? Is this outside of the scope of a 3d renderer and should be on the engine side? I'd love to receive and kind of advice or suggestions!
Thanks!
• By nedondev
I 'm learning how to create game by using opengl with c/c++ coding, so here is my fist game. In video description also have game contain in Dropbox. May be I will make it better in future.
Thanks.

• So I've recently started learning some GLSL and now I'm toying with a POM shader. I'm trying to optimize it and notice that it starts having issues at high texture sizes, especially with self-shadowing.
Now I know POM is expensive either way, but would pulling the heightmap out of the normalmap alpha channel and in it's own 8bit texture make doing all those dozens of texture fetches more cheap? Or is everything in the cache aligned to 32bit anyway? I haven't implemented texture compression yet, I think that would help? But regardless, should there be a performance boost from decoupling the heightmap? I could also keep it in a lower resolution than the normalmap if that would improve performance.
Any help is much appreciated, please keep in mind I'm somewhat of a newbie. Thanks!

• Hi,
I'm trying to learn OpenGL through a website and have proceeded until this page of it. The output is a simple triangle. The problem is the complexity.
I have read that page several times and tried to analyse the code but I haven't understood the code properly and completely yet. This is the code: