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60 lines
1.9 KiB
C++
60 lines
1.9 KiB
C++
// SPDX-License-Identifier: MIT
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#ifndef RGBDS_GFX_RGBA_HPP
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#define RGBDS_GFX_RGBA_HPP
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#include <stdint.h>
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struct Rgba {
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uint8_t red;
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uint8_t green;
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uint8_t blue;
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uint8_t alpha;
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constexpr Rgba(uint8_t r, uint8_t g, uint8_t b, uint8_t a)
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: red(r), green(g), blue(b), alpha(a) {}
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// Constructs the color from a "packed" RGBA representation (0xRRGGBBAA)
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explicit constexpr Rgba(uint32_t rgba = 0)
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: red(rgba >> 24), green(rgba >> 16), blue(rgba >> 8), alpha(rgba) {}
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static constexpr Rgba fromCGBColor(uint16_t color) {
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constexpr auto _5to8 = [](uint8_t channel) -> uint8_t {
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channel &= 0b11111; // For caller's convenience
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return channel << 3 | channel >> 2;
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};
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return {
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_5to8(color),
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_5to8(color >> 5),
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_5to8(color >> 10),
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static_cast<uint8_t>(color & 0x8000 ? 0x00 : 0xFF),
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};
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}
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// Returns this RGBA as a 32-bit number that can be printed in hex (`%08x`) to yield its CSS
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// representation
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uint32_t toCSS() const {
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constexpr auto shl = [](uint8_t val, unsigned shift) {
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return static_cast<uint32_t>(val) << shift;
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};
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return shl(red, 24) | shl(green, 16) | shl(blue, 8) | shl(alpha, 0);
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}
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bool operator==(Rgba const &rhs) const { return toCSS() == rhs.toCSS(); }
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// CGB colors are RGB555, so we use bit 15 to signify that the color is transparent instead
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// Since the rest of the bits don't matter then, we return 0x8000 exactly.
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static constexpr uint16_t transparent = 0b1'00000'00000'00000;
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static constexpr uint8_t transparency_threshold = 0x10;
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bool isTransparent() const { return alpha < transparency_threshold; }
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static constexpr uint8_t opacity_threshold = 0xF0;
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bool isOpaque() const { return alpha >= opacity_threshold; }
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// Computes the equivalent CGB color, respects the color curve depending on options
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uint16_t cgbColor() const;
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bool isGray() const { return red == green && green == blue; }
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uint8_t grayIndex() const;
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};
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#endif // RGBDS_GFX_RGBA_HPP
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