我试图通过利用freetype字形提供的位图缓冲区在opengl中渲染单个char作为演示。我知道我的三角扇是正确的，因为现在我看到一个黑色纹理triangle_fan绿色背景。理想情况下，我应该在triangle_fan原语中看到一个字符，而不仅仅是一个完整的实心黑色方块。
void fontDataNums_init(const char * fname) {
float h = font.h = 16;
/*Dynamically allocated variables, clean before exit */
FT_Face face;
FT_Library library;
GLubyte * expanded_data;
/* Create And Initilize A FreeType Font Library. */
if(FT_Init_FreeType( &library )) {
printf("fontDataNums_init::FT_Init_FreeType failed\n");
exit(1);
}
/* Initialize face, load font from ttf file */
if(FT_New_Face( library, fname, 0, &face )){
printf("fontDataNums_init::FT_New_Face failed\n");
exit(1);
}
if(FT_Set_Char_Size( face, h * 64, h * 64, 96, 96)){
printf("fontDataNums_init::FT_Set_Char_Size failed.\n");
exit(1);
}
font.textures = (GLuint *) malloc(sizeof(GLuint) * 10);
glGenTextures(10, font.textures);
/* CREATE CHARACTER BITMAPS I WANT LOADED */
unsigned char g;
int i, j;
for( g='A'; g < 'J'; g++){
if(FT_Load_Char(face, g, FT_LOAD_RENDER)){
printf("fontDataNums::FT_Load_Char unable to load glyph for character\n");
exit(1);
}
FT_Glyph glyph;
if(FT_Get_Glyph(face->glyph, &glyph) ) { printf("GetGlyph failed.\n");}
if(FT_Glyph_To_Bitmap(&glyph, ft_render_mode_normal, 0, 1)){
printf("fontDataNums::FT_Glyph_To_Bitmap failed to create bitmap.\n");
exit(1);
}
FT_BitmapGlyph bitmap_glyph = (FT_BitmapGlyph)glyph;
int width = next_p2( bitmap_glyph->bitmap.width );
int height = next_p2( bitmap_glyph->bitmap.rows );
printf("WIDTH: %i and HEIGHT: %i \n", width, height);
/* PADDING FOR BITMAP */
expanded_data = (GLubyte *) malloc(sizeof(GLubyte) * 2 * width * height);
for(j=0; j <height;j++) {
for(i=0; i < width; i++){
expanded_data[2*(i+j*width)] = expanded_data[2*(i+j*width)+1] =
(i>=bitmap_glyph->bitmap.width || j>=bitmap_glyph->bitmap.rows) ?
0 :
bitmap_glyph->bitmap.buffer[i + bitmap_glyph->bitmap.width*j];
}
}
/* LOAD TEXTURE INTO OPENGL */
glActiveTexture(GL_TEXTURE0);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glBindTexture( GL_TEXTURE_2D, font.textures[g]);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_LUMINANCE_ALPHA, GL_UNSIGNED_BYTE, expanded_data );
free(expanded_data);
FT_Done_Glyph(glyph);
}
/* Clean Up */
FT_Done_Face(face);
FT_Done_FreeType(library);
}
int next_p2 (int a )
{
int rval=1;
/* rval<<=1 Is A Prettier Way Of Writing rval*=2; */
while(rval<a) rval<<=1;
return rval;
}
void drawGlyph(){
renderGlyph(font.textures[1]);
}
void renderGlyph(GLuint textureName) {
GLuint tbo = 0;
GLuint vbo = 0;
glClear(GL_COLOR_BUFFER_BIT);
/* SETUP VERTICES */
GLfloat verts[8]={ 0.0f, 16.0f,
0.0f, 0.0f,
17.0f , 0.0f,
17.0f , 16.0f};
glEnableVertexAttribArray(GLT_ATTRIBUTE_VERTEX);
if(vbo == 0){glGenBuffers(1, &vbo);}
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 8, verts, GL_DYNAMIC_DRAW);
glVertexAttribPointer(GLT_ATTRIBUTE_VERTEX, 2, GL_FLOAT, GL_FALSE, 0, 0);
/* Setup Texture Buffer */
float x = 17.0f / 32.0f;
float y = 16.0f / 16.0f;
GLfloat vTex[8] = { 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f };
glEnableVertexAttribArray(GLT_ATTRIBUTE_TEXTURE0);
if(tbo == 0) { glGenBuffers(1, &tbo);}
glBindBuffer(GL_ARRAY_BUFFER, tbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 8, vTex, GL_DYNAMIC_DRAW);
glVertexAttribPointer(GLT_ATTRIBUTE_TEXTURE0, 2, GL_FLOAT, GL_FALSE, 0, 0);
/*Create Shaders*/
static const char *szIdentityShaderVP =
"#version 330\n"
"in vec4 vVertex;\n"
"in vec2 TexCoords;\n"
"out vec2 varyingTexCoords;\n"
"uniform mat4 mvp;\n"
"void main(void) \n"
"{"
"varyingTexCoords = TexCoords;\n"
"gl_Position = mvp * vVertex;\n"
"}\n";
static const char *szIdentityShaderFP =
"#version 330\n"
"uniform sampler2D colormap;\n"
"uniform vec4 showFan;"
"in vec2 varyingTexCoords;\n"
"void main(void) \n"
"{"
//"gl_FragColor = showFan;\n"
"gl_FragColor = texture(colormap, varyingTexCoords);\n"
"}\n";
GLuint shaderName = 0;
shaderName = gltLoadShaderPairSrcWithAttributes(szIdentityShaderVP, szIdentityShaderFP, 2, GLT_ATTRIBUTE_VERTEX, "vVertex", GLT_ATTRIBUTE_TEXTURE0, "TexCoords");
if(shaderName == 0) { printf("***shader compile failed****\n");}
glUseProgram(shaderName);
vmathM4MakeOrthographic( &pmatrix, -50.0f, 50.0f, -50.0f, 50.0f, -50.0f, 50.0f);
GLint mvp = 0;
mvp = glGetUniformLocation(shaderName, "mvp");
glUniformMatrix4fv(mvp, 1, GL_FALSE, (GLfloat *) &pmatrix);
GLint texUniform = 0;
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, textureName);
texUniform = glGetUniformLocation(shaderName, "colormap");
glUniform1i(texUniform, 0);
GLint showFan= 0;
showFan = glGetUniformLocation(shaderName, "showFan");
glUniform4f(showFan, 1.0f, 0.0f, 0.0f, 1.0f);
glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
SDL_GL_SwapWindow(gcore.mainwindow);
glDisableVertexAttribArray(GLT_ATTRIBUTE_VERTEX);
glDisableVertexAttribArray(GLT_ATTRIBUTE_TEXTURE0);
glDeleteProgram(shaderName);
glDeleteBuffers(1, &vbo);
glDeleteBuffers(1, &tbo);
glCheckError();
}
void glCheckError(){
GLenum checkError = glGetError();
if(checkError != GL_NO_ERROR)
printf("Error: %i\n", checkError);
}
答案 0 :(得分：1)
我在iPhone设备中使用freetype，它可以用...创建纹理
glTexImage2D( GL_TEXTURE_2D, 0, GL_LUMINANCE_ALPHA, width, height, 0, GL_LUMINANCE_ALPHA, GL_UNSIGNED_BYTE, data);