Simple atlas generator for Proggy Clean (and other monospace bitmap fonts)

atlasgen.cpp

#include <Windows.h>
#include <gdiplus.h>
#include <stdio.h>

#pragma comment(lib,"gdiplus.lib")
using namespace Gdiplus;

// https://docs.microsoft.com/en-us/windows/win32/gdiplus/-gdiplus-retrieving-the-class-identifier-for-an-encoder-use
int GetEncoderClsid(const WCHAR* format, CLSID* pClsid) {
    UINT  num = 0;          // number of image encoders
    UINT  size = 0;         // size of the image encoder array in bytes

    ImageCodecInfo* pImageCodecInfo = NULL;

    GetImageEncodersSize(&num, &size);
    if (size == 0)
        return -1;  // Failure

    pImageCodecInfo = (ImageCodecInfo*)(malloc(size));
    if (pImageCodecInfo == NULL)
        return -1;  // Failure

    GetImageEncoders(num, size, pImageCodecInfo);

    for (UINT j = 0; j < num; ++j)
    {
        if (wcscmp(pImageCodecInfo[j].MimeType, format) == 0)
        {
            *pClsid = pImageCodecInfo[j].Clsid;
            free(pImageCodecInfo);
            return j;  // Success
        }
    }

    free(pImageCodecInfo);
    return -1;  // Failure
}

int main() {
    // Init GDI+
    GdiplusStartupInput gdiplusStartupInput;
    ULONG_PTR gdiplusToken;
    GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);

    // Calculate how the texture will be generated
    constexpr unsigned char_width = 8;
    constexpr unsigned char_height = 8;
    constexpr unsigned char_underhang = 4;
    constexpr unsigned padding = 1;
    constexpr unsigned per_row = 16;
    constexpr unsigned rows = (128 - 32) / per_row + ((128 - 32) % per_row != 0);
    unsigned tex_width = (char_width + padding) * per_row;
    unsigned tex_height = (char_height + char_underhang + padding) * rows;
    printf("width: %d, height: %d\n", tex_width, tex_height);

    // Initialize the GDI objects
    SolidBrush brush(Color(255, 255, 255, 255));
    Bitmap atlas(tex_width, tex_height, PixelFormat32bppARGB);
    Graphics gfx(&atlas);
    FontFamily family(L"ProggyCleanTTSZ");
    Font font(&family, 16, FontStyleRegular, UnitPixel);

    // Render the atlas
    gfx.Clear(Color(0, 0, 0, 0));
    gfx.SetTextRenderingHint(TextRenderingHintSingleBitPerPixel);
    wchar_t buf[2] = {};
    for (int y = 0; y < rows; y++) {
        for (int x = 0; x < per_row; x++) {
            PointF point((char_width + padding) * x - 3.0f, (char_height + char_underhang + padding) * y - 2.0f);
            buf[0] = (wchar_t)(y * per_row + x + 32);
            gfx.DrawString(buf, -1, &font, point, &brush);
        }
    }

    /*
    // Save as a PNG file
    CLSID png_clsid;
    GetEncoderClsid(L"image/png", &png_clsid);
    atlas.Save(L"atlas.png", &png_clsid, NULL);
    */

    // Compress the atlas
    Rect rect(0, 0, tex_width, tex_height);
    BitmapData data;
    atlas.LockBits(&rect, ImageLockModeRead, PixelFormat32bppARGB, &data);
    unsigned compressed_size = tex_width * tex_height / 8 + (tex_width * tex_height % 8 != 0);
    char* compressed = new char[compressed_size];
    unsigned bits_left = tex_width * tex_height;
    for (unsigned i = 0; i < compressed_size; i++) {
        char output = 0;
        for (int j = 0; j < min(8, bits_left); j++) {
            output <<= 1;
            output |= ((char*)data.Scan0)[(i * 8 + j) * 4] != 0;
        }
        compressed[i] = output;
        bits_left -= 8;
    }
    atlas.UnlockBits(&data);

    // Save it
    FILE* output = fopen("atlas.bin", "wb");
    fwrite(compressed, compressed_size, 1, output);
    fclose(output);

    printf("Done\n");
    delete[] compressed;
    return 0;
}