texture_atlas_maker.hpp

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// This file is part of the Rendering Engine project.
// Author: Alexander Obzherin <alexanderobzherin@gmail.com>
// Copyright (c) 2026 Alexander Obzherin
// Distributed under the terms of the zlib License. See LICENSE.md for details.
#pragma once
 
#include <iostream>
#include <unordered_map>
#include <map>
#include <memory>
#include <fstream>
#include <sstream>
#include <filesystem>
#include "image_data.hpp"
#include "rendering_engine_export.hpp"
 
namespace rendering_engine
{
 
struct GlyphMetrics;
 
/**
 * @class TextureAtlasMaker
 * @brief Builds texture atlases from collections of images.
 *
 * Arranges input images into a grid-based atlas, aiming for a compact,
 * near-square layout. Supports generic image atlases and font glyph atlases.
 */
class RE_API TextureAtlasMaker
{
public:
    /**
     * @brief Constructs an atlas maker from a collection of images.
     * @param images Map of identifiers to image data.
     */
    TextureAtlasMaker(std::map<char, ImageData> images);
    ~TextureAtlasMaker() = default;
 
    /**
     * @brief Creates a texture atlas from the stored image collection.
     * @param texAtlasData Output map of image identifiers to atlas positions.
     * @param texAtlasImage Output atlas image.
     * @return True if the atlas was created successfully.
     */
    bool CreateTextureAtlas( std::map<char, std::pair<unsigned int, unsigned int>>& texAtlasData, ImageData& texAtlasImage );
 
    /**
     * @brief Creates a texture atlas from glyph images and updates glyph metrics.
     *
     * Modifies glyph metrics in-place to include atlas coordinates.
     *
     * @param ioFontAtlas Map of glyph identifiers to glyph metrics and images.
     * @return Generated atlas image.
     */
    static ImageData CreateTextureAtlas(std::unordered_map<std::uint32_t, std::pair<GlyphMetrics, ImageData>>& ioFontAtlas);
 
protected:
    /**
     * @brief Computes maximum cell dimensions for the stored images.
     * @param outputWidth Output cell width in pixels.
     * @param outputHeight Output cell height in pixels.
     */
    void FindCellDimensions(unsigned int& outputWidth, unsigned int& outputHeight);
 
    /**
     * @brief Computes maximum cell dimensions for glyph images.
     * @param outputWidth Output cell width in pixels.
     * @param outputHeight Output cell height in pixels.
     * @param fontAtlas Glyph image collection.
     */
    static void FindCellDimensions(unsigned int& outputWidth, unsigned int& outputHeight, std::unordered_map<std::uint32_t, std::pair<GlyphMetrics, ImageData>>& fontAtlas);
 
    /**
     * @brief Calculates grid dimensions for the stored images.
     * @param outputNumberOfColumns Output number of columns.
     * @param outputNumberOfRows Output number of rows.
     */
    void CalculateGridDimensions(unsigned int& outputNumberOfColumns, unsigned int& outputNumberOfRows);
 
    /**
     * @brief Calculates grid dimensions for glyph images.
     * @param outputNumberOfColumns Output number of columns.
     * @param outputNumberOfRows Output number of rows.
     * @param fontAtlas Glyph image collection.
     */
    static void CalculateGridDimensions(unsigned int& outputNumberOfColumns, unsigned int& outputNumberOfRows, std::unordered_map<std::uint32_t, std::pair<GlyphMetrics, ImageData>>& fontAtlas);
 
private:
    TextureAtlasMaker( TextureAtlasMaker const& );
    TextureAtlasMaker operator=(TextureAtlasMaker const&);
 
protected:
    //container of images
    std::map<char, ImageData> mImageCollection;
 
    static const Color sDefaultPaletteBackgroundColor;
};
 
} //namespace rendering_engine