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src/pvpngreader.h

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+// pngreader.h - Public Domain - see unlicense at bottom of pvpngreader.cpp
+#pragma once
+#include <stdint.h>
+
+namespace pv_png
+{
+	// PNG color types
+	enum
+	{
+		PNG_COLOR_TYPE_GREYSCALE = 0,
+		PNG_COLOR_TYPE_TRUECOLOR = 2,
+		PNG_COLOR_TYPE_PALETTIZED = 3,
+		PNG_COLOR_TYPE_GREYSCALE_ALPHA = 4,
+		PNG_COLOR_TYPE_TRUECOLOR_ALPHA = 6
+	};
+
+	// PNG file description
+	struct png_info
+	{
+		uint32_t m_width;
+		uint32_t m_height;
+				
+		uint32_t m_num_chans;	// The number of channels, factoring in transparency. Ranges from [1-4].
+
+		uint32_t m_bit_depth;	// PNG ihdr bit depth: 1, 2, 4, 8 or 16
+		uint32_t m_color_type;	// PNG ihdr color type, PNG_COLOR_TYPE_GRAYSCALE etc.
+
+		bool m_has_gamma;		// true if the PNG file had a GAMA chunk
+		uint32_t m_gamma_value; // PNG GAMA chunk value, scaled by 100000
+
+		bool m_has_trns;		// true if the PNG file used colorkey transparency
+	};
+
+	// Retrieved information about the PNG file.
+	// Returns false on any errors.
+	bool get_png_info(const void* pImage_buf, size_t buf_size, png_info& info);
+
+	// Input parameters:
+	// pImage_buf, buf_size - pointer to PNG image data
+	// desired_chans - desired number of output channels. 0=auto, 1=grayscale, 2=grayscale alpha, 3=24bpp RGB, 4=32bpp RGBA
+	//
+	// Output parameters:
+	// width, height - PNG image resolution
+	// num_chans - actual number of channels in PNG, from [1,4] (factoring in transparency)
+	//
+	// Returns nullptr on any errors.
+	void* load_png(const void* pImage_buf, size_t buf_size, uint32_t desired_chans, uint32_t &width, uint32_t &height, uint32_t& num_chans);
+}