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81 lines
3.3 KiB
C++
81 lines
3.3 KiB
C++
// -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
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// Copyright (C) 2014 Henner Zeller <h.zeller@acm.org>
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//
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation version 2.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://gnu.org/licenses/gpl-2.0.txt>
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#ifndef RPI_CANVAS_H
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#define RPI_CANVAS_H
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#include <stdint.h>
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namespace rgb_matrix {
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// An interface for things a Canvas can do. The RGBMatrix implements this
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// interface, so you can use it directly wherever a canvas is needed.
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//
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// This abstraction also allows you to e.g. create delegating
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// implementations that do a particular transformation, e.g. re-map
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// pixels (as you might lay out the physical RGB matrix in a different way),
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// compose images (OR, XOR, transparecy), scale, rotate, anti-alias or
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// translate coordinates in a funky way.
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//
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// It is a good idea to have your applications use the concept of
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// a Canvas to write the content to instead of directly using the RGBMatrix.
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class Canvas {
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public:
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virtual ~Canvas() {}
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virtual int width() const = 0; // Pixels available in x direction.
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virtual int height() const = 0; // Pixels available in y direction.
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// Set pixel at coordinate (x,y) with given color. Pixel (0,0) is the
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// top left corner.
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// Each color is 8 bit (24bpp), 0 black, 255 brightest.
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virtual void SetPixel(int x, int y,
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uint8_t red, uint8_t green, uint8_t blue) = 0;
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// Clear screen to be all black.
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virtual void Clear() = 0;
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// Fill screen with given 24bpp color.
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virtual void Fill(uint8_t red, uint8_t green, uint8_t blue) = 0;
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};
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// A canvas transformer is an object that, given a Canvas, returns a
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// canvas that applies transformations before writing to the original
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// Canvas.
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//
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// To simplify assumptions for implementations and users of implementations,
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// the following conditions and constraints apply:
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//
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// 1) The CanvasTransformer _never_ takes ownership of the delegatee.
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// 2) The ownership of the returned Canvas is _not_ passed to the caller.
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// 3) The returned Canvas can only be assumed to be valid for the lifetime
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// of the CanvasTranformer and the lifetime of the original canvas.
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// 4) The returned canvas is only valid up to the next call of Transform().
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//
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// * Point 2)-4) imply that the CanvasTransformer can hand out the same
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// canvas object every time, just configured to write to the new
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// delegatee.
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// * Point 4) implies that one instance of CanvasTransformer cannot be used in
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// parallel in multiple threads calling Transform().
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// * The constraints also imply that it is valid for a CanvasTransformer to
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// return the passed in canvas itself.
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class CanvasTransformer {
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public:
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virtual ~CanvasTransformer() {}
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// Return a Canvas* that applies transformations before delegating to
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// the output canvas.
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virtual Canvas *Transform(Canvas *output) = 0;
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};
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} // namespace rgb_matrix
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#endif // RPI_CANVAS_H
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