53 lines
1.8 KiB
C++
53 lines
1.8 KiB
C++
/*
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* Copyright 2016 - 2022 Gary Talent (gary@drinkingtea.net). All rights reserved.
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*/
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#pragma once
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#include <nostalgia/geo/point.hpp>
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#include "consts.hpp"
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namespace nostalgia::core {
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[[nodiscard]]
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constexpr std::size_t ptToIdx(int x, int y, int c) noexcept {
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constexpr auto colLength = static_cast<std::size_t>(PixelsPerTile);
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const auto rowLength = static_cast<std::size_t>(static_cast<std::size_t>(c / TileWidth) * colLength);
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const auto colStart = static_cast<std::size_t>(colLength * static_cast<std::size_t>(x / TileWidth));
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const auto rowStart = static_cast<std::size_t>(rowLength * static_cast<std::size_t>(y / TileHeight));
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const auto colOffset = static_cast<std::size_t>(x % TileWidth);
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const auto rowOffset = static_cast<std::size_t>(static_cast<std::size_t>(y % TileHeight) * TileHeight);
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return static_cast<std::size_t>(colStart + colOffset + rowStart + rowOffset);
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}
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[[nodiscard]]
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constexpr std::size_t ptToIdx(const geo::Point &pt, int c) noexcept {
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return ptToIdx(pt.x, pt.y, c * TileWidth);
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}
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[[nodiscard]]
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constexpr geo::Point idxToPt(int i, int c) noexcept {
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const auto t = i / PixelsPerTile; // tile number
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const auto iti = i % PixelsPerTile; // in tile index
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const auto tc = t % c; // tile column
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const auto tr = t / c; // tile row
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const auto itx = iti % TileWidth; // in tile x
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const auto ity = iti / TileHeight; // in tile y
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return {
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itx + tc * TileWidth,
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ity + tr * TileHeight,
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};
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}
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static_assert(idxToPt(4, 1) == geo::Point{4, 0});
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static_assert(idxToPt(8, 1) == geo::Point{0, 1});
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static_assert(idxToPt(8, 2) == geo::Point{0, 1});
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static_assert(idxToPt(64, 2) == geo::Point{8, 0});
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static_assert(idxToPt(128, 2) == geo::Point{0, 8});
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static_assert(idxToPt(129, 2) == geo::Point{1, 8});
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static_assert(idxToPt(192, 2) == geo::Point{8, 8});
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static_assert(idxToPt(384, 8) == geo::Point{48, 0});
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}
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