Texture.h

/*
 * Gamedev Framework (gf)
 * Copyright (C) 2016 Julien Bernard
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 *
 * Part of this file comes from SFML, with the same license:
 * Copyright (C) 2007-2015 Laurent Gomila (laurent@sfml-dev.org)
 */
#ifndef GF_TEXTURE_H
#define GF_TEXTURE_H

#include <cstdint>

#include "Filesystem.h"
#include "Portability.h"
#include "Rect.h"
#include "Vector.h"

namespace gf {
#ifndef DOXYGEN_SHOULD_SKIP_THIS
inline namespace v1 {
#endif

  class Image;
  class InputStream;

  /**
   * @ingroup graphics
   * @brief An image that lives in the graphic memory that can be used for drawing
   *
   * gf::BareTexture stores pixels that can be drawn, with a sprite
   * for example. A texture lives in the graphics card memory,
   * therefore it is very fast to draw a texture to a render target,
   * or copy a render target to a texture (the graphics card can
   * access both directly).
   *
   * Being stored in the graphics card memory has some drawbacks.
   * A texture cannot be manipulated as freely as a gf::Image,
   * you need to prepare the pixels first and then upload them
   * to the texture in a single operation (see BareTexture::update()).
   *
   * gf::BareTexture can handle two types of texture:
   *
   * - colored texture that stores RGBA channels (see gf::Texture)
   * - alpha texture that stores a single alpha channel (see gf::FontTexture)
   *
   * Generally, you do not manipulated a gf::BareTexture directly but you can
   * use a gf::Texture.
   *
   * @sa gf::Texture, gf::AlphaTexture
   */
  class GF_API BareTexture {
  public:
    /**
     * @brief Format of the texture
     *
     * @sa gf::BareTexture
     */
    enum class Format {
      Color, ///< RGBA format
      Alpha, ///< Alpha format
    };

    /**
     * @brief Constructor
     *
     * @param format The format of the texture
     *
     * Once set, the format can not be changed.
     */
    BareTexture(Format format);

    /**
     * @brief Destructor
     */
    ~BareTexture();

    /**
     * @brief Deleted copy constructor
     */
    BareTexture(const BareTexture&) = delete;

    /**
     * @brief Deleted copy assignment
     */
    BareTexture& operator=(const BareTexture&) = delete;

    /**
     * @brief Move constructor
     */
    BareTexture(BareTexture&& other);

    /**
     * @brief Move assignment
     */
    BareTexture& operator=(BareTexture&& other);

    /**
     * @brief Get the format of the texture
     *
     * @return The format of the texture
     */
    Format getFormat() const {
      return m_format;
    }

    /**
     * @brief Get the internal representation of the texture
     *
     * This function is for internal use only.
     *
     * @return The OpenGL name of the texture
     */
    unsigned getName() const {
      return m_name;
    }

    /**
     * @brief Return the size of the texture
     *
     * @return Size in pixels
     */
    Vector2u getSize() const {
      return m_size;
    }

    /**
     * @brief Enable or disable the smooth filter
     *
     * When the filter is activated, the texture appears smoother
     * so that pixels are less noticeable. However if you want
     * the texture to look exactly the same as its source file,
     * you should leave it disabled.
     *
     * The smooth filter is disabled by default.
     *
     * @param smooth True to enable smoothing, false to disable it
     *
     * @see isSmooth()
     */
    void setSmooth(bool smooth = true);

    /**
     * @brief Check if the smooth filter is enabled or not
     *
     * @return True if smoothing is enabled, false if it is disabled
     *
     * @see setSmooth()
     */
    bool isSmooth() const noexcept {
      return m_smooth;
    }

    /**
     * @brief Enable or disable repeating
     *
     * Repeating is involved when using texture coordinates
     * outside the texture rectangle @f$ [0, 1] @times [0, 1] @f$.
     * In this case, if repeat mode is enabled, the whole texture
     * will be repeated as many times as needed to reach the
     * coordinate (for example, if the @f$ u @f$ texture coordinate is
     * 3, the texture will be repeated 3 times).
     *
     * If repeat mode is disabled, the "extra space" will instead
     * be filled with border pixels.
     *
     * Repeating is disabled by default.
     *
     * @param repeated True to repeat the texture, false to disable repeating
     *
     * @see isRepeated()
     */
    void setRepeated(bool repeated = true);

    /**
     * @brief Check if the texture is repeated or not
     *
     * @return True if repeat mode is enabled, false if it is disabled
     *
     * @see setRepeated()
     */
    bool isRepeated() const noexcept {
      return m_repeated;
    }

    /**
     * @brief Update the whole texture from an array of pixels
     *
     * The `data` array is assumed to be in the right format (4 channels
     * for colored texture and 1 channel for alpha texture) and have the
     * right size.
     *
     * No additional check is performed on the size of the pixel
     * array, passing invalid arguments will lead to an undefined
     * behavior.
     *
     * This function does nothing if `data` is `nullptr` or if the
     * texture was not previously created.
     *
     * @param data An array of pixels to copy to the texture
     */
    void update(const uint8_t *data);

    /**
     * @brief Update a part of the texture from an array of pixels
     *
     * The `data` array is assumed to be in the right format (4 channels
     * for colored texture and 1 channel for alpha texture) and its size
     * must match the size of the `rect` argument.
     *
     * No additional check is performed on the size of the pixel
     * array or the bounds of the area to update, passing invalid
     * arguments will lead to an undefined behavior.
     *
     * This function does nothing if `data` is `nullptr` or if the
     * texture was not previously created.
     *
     * @param data An array of pixels to copy to the texture
     * @param rect The region of the texture to update
     */
    void update(const uint8_t *data, const RectU& rect);

    /**
     * @brief Compute normalized texture coordinates
     *
     * @param rect The rectangle in the texture, in pixels
     * @return Normalized texture coordinates
     */
    RectF computeTextureCoords(const RectU& rect) const;

    /**
     * @brief Generate a mipmap using the current texture data
     *
     * Mipmaps are pre-computed chains of optimized textures. Each
     * level of texture in a mipmap is generated by halving each of
     * the previous level's dimensions. This is done until the final
     * level has the size of 1x1. The textures generated in this process may
     * make use of more advanced filters which might improve the visual quality
     * of textures when they are applied to objects much smaller than they are.
     * This is known as minification. Because fewer texels (texture elements)
     * have to be sampled from when heavily minified, usage of mipmaps
     * can also improve rendering performance in certain scenarios.
     *
     * Mipmap data is only valid from the time it is generated until the next
     * time the base level image is modified, at which point this function
     * will have to be called again to regenerate it.
     *
     * @return True if mipmap generation was successful, false if unsuccessful
     */
    bool generateMipmap();

    /**
     * @brief Bind a texture for rendering
     *
     * This function is for internal use only.
     *
     * @param texture Pointer to the texture to bind, can be `nullptr` to use no texture
     */
    static void bind(const BareTexture *texture);

  protected:
    /**
     * @brief Create the texture
     *
     * If this function fails, the texture is left unchanged.
     *
     * @param size Size of the texture
     * @param data Initial pixels of the texture (can be `nullptr`)
     *
     * @return True if creation was successful
     */
    bool create(Vector2u size, const uint8_t *data);

  private:
    Format m_format;
    unsigned m_name;
    Vector2u m_size;
    bool m_smooth;
    bool m_repeated;
    bool m_mipmap;
  };


  /**
   * @ingroup graphics
   * @brief A texture for colored images
   *
   * A texture can be loaded from an image, but also directly
   * from a file/memory/stream. The necessary shortcuts are defined
   * so that you don't need an image first for the most common cases.
   * However, if you want to perform some modifications on the pixels
   * before creating the final texture, you can load your file to a
   * gf::Image, do whatever you need with the pixels, and then call
   * Texture::loadFromImage.
   *
   * Like gf::Image, gf::Texture can handle a unique internal
   * representation of pixels, which is RGBA. This means
   * that a pixel must be composed of 8 bits red, green, blue and
   * alpha channels.
   *
   * Usage example:
   *
   * ~~~{.cc}
   * // This example shows the most common use of gf::Texture:
   * // drawing a sprite
   *
   * // Load a texture from a file
   * gf::Texture texture;
   *
   * if (!texture.loadFromFile("texture.png")) {
   *   return -1;
   * }
   *
   * // Assign it to a sprite
   * gf::Sprite sprite;
   * sprite.setTexture(texture);
   *
   * // Draw the textured sprite
   * window.draw(sprite);
   * ~~~
   *
   * @sa gf::Sprite, gf::Image, gf::RenderTexture
   */
  class GF_API Texture : public BareTexture {
  public:
    /**
     * @brief Constructor
     *
     * No texture is created.
     */
    Texture();

    /**
     * @brief Create the texture
     *
     * If this function fails, the texture is left unchanged.
     *
     * @param size Size of the texture
     *
     * @return True if creation was successful
     */
    bool create(Vector2u size);

    /**
     * @brief Load the texture from an image
     *
     * If this function fails, the texture is left unchanged.
     *
     * @param image Image to load into the texture
     *
     * @return True if loading was successful
     *
     * @sa loadFromFile(), loadFromMemory(), loadFromStream()
     */
    bool loadFromImage(const Image& image);

    /**
     * @brief Load the texture from a file on disk
     *
     * This function is a shortcut for the following code:
     *
     * ~~~{.cc}
     * gf::Image image;
     * image.loadFromFile(filename);
     * texture.loadFromImage(image);
     * ~~~
     *
     * If this function fails, the texture is left unchanged.
     *
     * @param filename Path of the image file to load
     *
     * @return True if loading was successful
     *
     * @sa loadFromMemory(), loadFromStream(), loadFromImage()
     */
    bool loadFromFile(const Path& filename);

    /**
     * @brief Load the texture from a custom stream
     *
     * This function is a shortcut for the following code:
     *
     * ~~~{.cc}
     * gf::Image image;
     * image.loadFromStream(stream);
     * texture.loadFromImage(image);
     * ~~~
     *
     * If this function fails, the texture is left unchanged.
     *
     * @param stream Source stream to read from
     * @return True if loading was successful
     *
     * @see loadFromFile(), loadFromMemory(), loadFromImage()
     */
    bool loadFromStream(InputStream& stream);

    /**
     * @brief Load the texture from a file in memory
     *
     * This function is a shortcut for the following code:
     *
     * ~~~{.cc}
     * gf::Image image;
     * image.loadFromMemory(data, length);
     * texture.loadFromImage(image);
     * ~~~
     *
     * If this function fails, the texture is left unchanged.
     *
     * @param data Pointer to the file data in memory
     * @param length Length of the data to load, in bytes
     * @return True if loading was successful
     *
     * @see loadFromFile(), loadFromStream(), loadFromImage()
     */
    bool loadFromMemory(const uint8_t *data, std::size_t length);

    /**
     * @brief Update the texture from an image
     *
     * Although the source image can be smaller than the texture,
     * this function is usually used for updating the whole texture.
     *
     * No additional check is performed on the size of the image,
     * passing an image bigger than the texture will lead to an
     * undefined behavior.
     *
     * This function does nothing if the texture was not
     * previously created.
     *
     * @param image Image to copy to the texture
     */
    void update(const Image& image);

    /**
     * @brief Copy the texture pixels to an image
     *
     * This function performs a slow operation that downloads
     * the texture's pixels from the graphics card and copies
     * them to a new image, potentially applying transformations
     * to pixels if necessary (texture may be padded or flipped).
     *
     * @return An image containing the texture's pixels
     * 
     * @sa loadFromImage()
     */
    Image copyToImage() const;

  };


  /**
   * @ingroup graphics
   * @brief A texture with a single alpha channel
   *
   * This texture is used internally by gf::Font
   */
  class GF_API AlphaTexture : public BareTexture {
  public:
    /**
     * @brief Constructor
     *
     * No texture is created
     */
    AlphaTexture();

    /**
     * @brief Create the texture
     *
     * If this function fails, the texture is left unchanged.
     *
     * @param size Size of the texture
     *
     * @return True if creation was successful
     */
    bool create(Vector2u size);
  };

#ifndef DOXYGEN_SHOULD_SKIP_THIS
}
#endif
}

#endif // GF_TEXTURE_H