nvidia-texture-tools/src/nvimage/Filter.h

// This code is in the public domain -- castanyo@yahoo.es

#ifndef NV_IMAGE_FILTER_H
#define NV_IMAGE_FILTER_H

#include <nvimage/nvimage.h>
#include <nvcore/Debug.h>

namespace nv
{
	class Vector4;

	/// Base filter class.
	class NVIMAGE_CLASS Filter
	{
	public:
		Filter(float width);
		virtual ~Filter();

		float width() const { return m_width; }
		float sampleDelta(float x, float scale) const;
		float sampleBox(float x, float scale, int samples) const;
		float sampleTriangle(float x, float scale, int samples) const;

		virtual float evaluate(float x) const = 0;

	protected:
		const float m_width;
	};

	// Box filter.
	class NVIMAGE_CLASS BoxFilter : public Filter
	{
	public:
		BoxFilter();
		BoxFilter(float width);
		virtual float evaluate(float x) const;
	};

	// Triangle (bilinear/tent) filter.
	class NVIMAGE_CLASS TriangleFilter : public Filter
	{
	public:
		TriangleFilter();
		TriangleFilter(float width);
		virtual float evaluate(float x) const;
	};

	// Quadratic (bell) filter.
	class NVIMAGE_CLASS QuadraticFilter : public Filter
	{
	public:
		QuadraticFilter();
		virtual float evaluate(float x) const;
	};

	// Cubic filter from Thatcher Ulrich.
	class NVIMAGE_CLASS CubicFilter : public Filter
	{
	public:
		CubicFilter();
		virtual float evaluate(float x) const;
	};

	// Cubic b-spline filter from Paul Heckbert.
	class NVIMAGE_CLASS BSplineFilter : public Filter
	{
	public:
		BSplineFilter();
		virtual float evaluate(float x) const;
	};

	/// Mitchell & Netravali's two-param cubic
	/// @see "Reconstruction Filters in Computer Graphics", SIGGRAPH 88
	class NVIMAGE_CLASS MitchellFilter : public Filter
	{
	public:
		MitchellFilter();
		virtual float evaluate(float x) const;

		void setParameters(float a, float b);

	private:
		float p0, p2, p3;
		float q0, q1, q2, q3;
	};

	// Lanczos3 filter.
	class NVIMAGE_CLASS LanczosFilter : public Filter
	{
	public:
		LanczosFilter();
		virtual float evaluate(float x) const;
	};

	// Sinc filter.
	class NVIMAGE_CLASS SincFilter : public Filter
	{
	public:
		SincFilter(float w);
		virtual float evaluate(float x) const;
	};

	// Kaiser filter.
	class NVIMAGE_CLASS KaiserFilter : public Filter
	{
	public:
		KaiserFilter(float w);
		virtual float evaluate(float x) const;
	
		void setParameters(float a, float stretch);

	private:
		float alpha;
		float stretch;
	};



	/// A 1D kernel. Used to precompute filter weights.
	class NVIMAGE_CLASS Kernel1
	{
		NV_FORBID_COPY(Kernel1);
	public:
		Kernel1(const Filter & f, int iscale, int samples = 32);
		~Kernel1();
		
		float valueAt(uint x) const {
			nvDebugCheck(x < (uint)m_windowSize);
			return m_data[x];
		}
		
		int windowSize() const {
			return m_windowSize;
		}
		
		float width() const {
			return m_width;
		}
		
		void debugPrint();
		
	private:
		int m_windowSize;
		float m_width;
		float * m_data;
	};


	/// A 2D kernel.
	class NVIMAGE_CLASS Kernel2 
	{
	public:
		Kernel2(uint width);
		Kernel2(const Kernel2 & k);
		~Kernel2();
		
		void normalize();
		void transpose();
		
		float valueAt(uint x, uint y) const {
			return m_data[y * m_windowSize + x];
		}
		
		uint windowSize() const {
			return m_windowSize;
		}
		
		void initLaplacian();
		void initEdgeDetection();
		void initSobel();
		void initPrewitt();
		
		void initBlendedSobel(const Vector4 & scale);
		
	private:
		const uint m_windowSize;
		float * m_data;
	};


	/// A 1D polyphase kernel
	class NVIMAGE_CLASS PolyphaseKernel
	{
		NV_FORBID_COPY(PolyphaseKernel);
	public:
		PolyphaseKernel(const Filter & f, uint srcLength, uint dstLength, int samples = 32);
		~PolyphaseKernel();
		
		int windowSize() const {
			return m_windowSize;
		}
		
		uint length() const {
			return m_length;
		}

		float width() const {
			return m_width;
		}

		float valueAt(uint column, uint x) const {
			nvDebugCheck(column < m_length);
			nvDebugCheck(x < (uint)m_windowSize);
			return m_data[column * m_windowSize + x];
		}

		void debugPrint() const;
		
	private:
		int m_windowSize;
		uint m_length;
		float m_width;
		float * m_data;
	};

} // nv namespace

#endif // NV_IMAGE_FILTER_H