Add easy sampling routines.

These can be used if you want them. Don't have to though.

include/pixel/RgbaColor.h

@@ -26,6 +26,15 @@ namespace pixel {
 	   public:
 		// maybe provide ctors?
 
+		constexpr RgbaColor() = default;
+
+		constexpr RgbaColor(std::uint8_t r, std::uint8_t g, std::uint8_t b, std::uint8_t a)
+			: r(r),
+			  g(g),
+			  b(b),
+			  a(a) {
+		}
+
 		struct {
 			std::uint8_t r;
 			std::uint8_t g;
@@ -39,8 +48,8 @@ namespace pixel {
 
 		// TODO: Maybe:
 		//
-		// RgbaColor ColorFrom16Bpp(uint16_t, endian);
-		// unique_ptr<RgbaColor[]> PaletteFrom16Bpp(span<const uint16_t>, endian);
+		static RgbaColor ColorFrom16Bpp(std::uint16_t);
+		static void PaletteFrom16Bpp(RgbaColor* dest, const std::uint8_t* src, std::size_t colorCount);
 	};
 } // namespace pixel
 

include/pixel/RgbaImage.h

@@ -82,10 +82,14 @@ namespace pixel {
 		 */
 		[[nodiscard]] ImageSize GetSize() const;
 
-		// TODO: Add these methods, to make sampling data a bit nicer.
-		//
-		// static RgbaImage From4Bpp(span<std::uint8_t> data, span<RgbaColor> palette, ImageSize size);
-		// static RgbaImage From8Bpp(span<std::uint8_t> data, span<RgbaColor> palette, ImageSize size);
+		// Methods for easy sampling/conversion.
+		// Note:
+		// Palette for all palletized formats is expected to have
+		// been converted via RgbaColor::PaletteFrom*Bpp() or
+		// already in RgbaColor format.
+
+		static RgbaImage From4Bpp(const std::uint8_t* data, const RgbaColor* palette, ImageSize size);
+		static RgbaImage From8Bpp(const std::uint8_t* data, const RgbaColor* palette, ImageSize size);
 		// static RgbaImage From16Bpp(span<std::uint8_t> data, ImageSize size);
 		// static RgbaImage From32Bpp(span<std::uint8_t> data, ImageSize size);
 

src/CMakeLists.txt

@@ -1,6 +1,7 @@
 add_library(pixel_libpixel
 		stb_impl.cpp
 
+		RgbaColor.cpp
 		RgbaImage.cpp
 		ImageWriter.cpp
 		)

src/RgbaColor.cpp

@@ -0,0 +1,32 @@
+//
+// libpixel
+//
+// (C) 2021-2022 modeco80 <lily.modeco80@protonmail.ch>
+//
+// SPDX-License-Identifier: LGPL-3.0-or-later
+//
+
+#include <pixel/RgbaColor.h>
+
+namespace pixel {
+
+	// could be made constexpr probably..
+
+	RgbaColor RgbaColor::ColorFrom16Bpp(std::uint16_t color) {
+		return {
+			static_cast<std::uint8_t>((color & 0x001F) << 3),
+			static_cast<std::uint8_t>((color & 0x03E0) >> 2),
+			static_cast<std::uint8_t>((color & 0x7C00) >> 7),
+			255
+		};
+	}
+
+	void RgbaColor::PaletteFrom16Bpp(RgbaColor* dest, const std::uint8_t* src, std::size_t colorCount) {
+		for(int i = 0; i < colorCount; ++i) {
+			const auto colorIndex = i * sizeof(std::uint16_t);
+			const std::uint16_t colorWord = (src[colorIndex + 1] << 8) | src[colorIndex];
+			dest[i] = RgbaColor::ColorFrom16Bpp(colorWord);
+		}
+	}
+
+} // namespace pixel

src/RgbaImage.cpp

@@ -55,4 +55,25 @@ namespace pixel {
 		return size;
 	}
 
+	RgbaImage RgbaImage::From4Bpp(const std::uint8_t* data, const RgbaColor* palette, ImageSize size) {
+		RgbaImage image(size);
+		auto* buffer = image.GetBuffer();
+
+		for(std::size_t i = 0; i < (size.width * size.height / 2); ++i)
+			for(std::size_t b = 0; b < 2; b++)
+				*(buffer++) = palette[static_cast<std::uint16_t>(((data[i] & (0x0F << (b * 4))) >> (b * 4)))];
+
+		return image;
+	}
+
+	RgbaImage RgbaImage::From8Bpp(const std::uint8_t* data, const RgbaColor* palette, ImageSize size) {
+		RgbaImage image(size);
+		auto* buffer = image.GetBuffer();
+
+		for(std::size_t i = 0; i < size.width * size.height; ++i)
+			*(buffer++) = palette[data[i]];
+
+		return image;
+	}
+
 } // namespace pixel