djstdlib/gfx/Texture.c

#include "Texture.h"
#include "../os.h"
#include <math.h>

Texture createTexture(const char* bitmap, int32 width, int32 height) {
    Texture result = {0};
    result.width = width;
    result.height = height;
    glGenTextures(1, &result.tex_id);
    glBindTexture(GL_TEXTURE_2D, result.tex_id);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, result.width, result.height, 0, GL_RGB, GL_UNSIGNED_BYTE, bitmap);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);	
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    glGenerateMipmap(GL_TEXTURE_2D);

    return result;
}

DefineList(stbtt_bakedchar, STBBakedChar);

static void saveGrayscaleTarga(string location, const char *bytes, int width, int height) {
    char tgaHeader[18] = {
        // Image ID length
        0x00,
        // Color map type
        0x00,
        // Image type
        0x03,
        // Color map info (unused)
        0x0, 0x0, 0x0, 0x0, 0x0,
        // Image spec
        0x0, 0x0, // x origin
        0x0, 0x0, // y origin
        width & 0xFF, (width >> 8) & 0xFF, // width
        height & 0xFF, (height >> 8) & 0xFF, // width
        0x8, // bits per px (depth)
        0b00000000, // image descriptor
    };
    os_writeEntireFile(location, tgaHeader, ArrayCount(tgaHeader));
    os_fileAppend(location, bytes, width * height);
}

Font createFont(Arena *arena, string ttfLocation, real32 lineHeight) {
    const int CODEPOINT_START = 32;
    const int CODEPOINT_END = 126;

    int32 atlasWidth = ((int32)lineHeight)*(int32)sqrt(CODEPOINT_END - CODEPOINT_START);
    int32 atlasHeight = ((int32)lineHeight)*(int32)sqrt(CODEPOINT_END - CODEPOINT_START);

    STBBakedCharList bakedCharlist = PushFullListZero(arena, STBBakedCharList, CODEPOINT_END - CODEPOINT_START);
    string fontFile = os_readEntireFile(arena, ttfLocation);

    stbtt_fontinfo info;
    stbtt_InitFont(&info, (unsigned char *)fontFile.str, stbtt_GetFontOffsetForIndex((unsigned char *)fontFile.str, 0));
    int ascent, descent, lineGap;
    stbtt_GetFontVMetrics(&info, &ascent, &descent, &lineGap);
    real32 scale = stbtt_ScaleForPixelHeight(&info, lineHeight);

    char *bakedFontBitmap = PushArrayZero(arena, char, atlasWidth*atlasHeight);
    int32 bake_result = stbtt_BakeFontBitmap(
            (unsigned char *)fontFile.str, 0,
            lineHeight,
            (unsigned char *)bakedFontBitmap, atlasWidth, atlasHeight,
            CODEPOINT_START, CODEPOINT_END - CODEPOINT_START,
            bakedCharlist.data);

    GlyphMetaList glyphMeta = PushFullListZero(arena, GlyphMetaList, bakedCharlist.length);
    real32 x, y;
    real32 lastX, lastY;
    for (EachIn(bakedCharlist, i)) {
        stbtt_aligned_quad q;
        stbtt_GetBakedQuad(bakedCharlist.data, atlasWidth, atlasHeight, i, &x, &y, &q, 1);
        glyphMeta.data[i] = (GlyphMeta){
            .uv0=(Vec2){q.s0, q.t1},
            .uv1=(Vec2){q.s1, q.t0},
            .xOffset=q.x0 - lastX,
            .yOffset=q.y0 + lineHeight + scale * descent,
            .width=q.x1-q.x0,
            .height=q.y1-q.y0,
        };
        lastX = x;
        lastY = y;
    }

    Font result = {0};
    result.glyphMeta = glyphMeta;
    result.lineHeight = lineHeight;
    result.charWidth = bakedCharlist.data[0].xadvance;

    //saveGrayscaleTarga(s("atlas.tga"), bakedFontBitmap, atlasWidth, atlasHeight);

    glGenTextures(1, &result.texId);
    glBindTexture(GL_TEXTURE_2D, result.texId);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, atlasWidth, atlasHeight, 0, GL_RED, GL_UNSIGNED_BYTE, bakedFontBitmap);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);	
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glGenerateMipmap(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, 0);

    glGenBuffers(1, &result.glyphTableBufId);
    glBindBuffer(GL_TEXTURE_BUFFER, result.glyphTableBufId);
    glBufferData(GL_TEXTURE_BUFFER, sizeof(result.glyphMeta.data[0])*result.glyphMeta.length, result.glyphMeta.data, GL_STATIC_DRAW);

    glGenTextures(1, &result.glyphTableTexId);
    glBindTexture(GL_TEXTURE_BUFFER, result.glyphTableTexId);
    glTexBuffer(GL_TEXTURE_BUFFER, GL_RGBA32F, result.glyphTableBufId);

    return result;
}

Texture createTextureFromFile(const char* source_path) {
    Texture result = {0};
    glGenTextures(1, &result.tex_id);
    glBindTexture(GL_TEXTURE_2D, result.tex_id);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);	
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    int nr_channels;
    stbi_uc *data = stbi_load(source_path, &result.width, &result.height, &nr_channels, 0);
    if (data) {
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, result.width, result.height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
        glGenerateMipmap(GL_TEXTURE_2D);
    } else {
        print("Failed to load texture.");
    }
    stbi_image_free(data);

    return result;
}