mirror of https://github.com/OpenRCT2/OpenRCT2.git
162 lines
4.0 KiB
C++
162 lines
4.0 KiB
C++
/*****************************************************************************
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* Copyright (c) 2014-2020 OpenRCT2 developers
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*
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* For a complete list of all authors, please refer to contributors.md
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* Interested in contributing? Visit https://github.com/OpenRCT2/OpenRCT2
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*
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* OpenRCT2 is licensed under the GNU General Public License version 3.
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*****************************************************************************/
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#include "Drawing.h"
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#include <cmath>
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#include <cstdlib>
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/**
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* Draws a horizontal line of specified colour to a buffer.
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* rct2: 0x0068474C
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*/
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static void gfx_draw_line_on_buffer(rct_drawpixelinfo* dpi, char colour, int32_t y, int32_t x, int32_t no_pixels)
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{
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y -= dpi->y;
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// Check to make sure point is in the y range
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if (y < 0)
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return;
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if (y >= dpi->height)
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return;
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// Check to make sure we are drawing at least a pixel
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if (!no_pixels)
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no_pixels++;
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x -= dpi->x;
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// If x coord outside range leave
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if (x < 0)
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{
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// Unless the number of pixels is enough to be in range
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no_pixels += x;
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if (no_pixels <= 0)
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return;
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// Resets starting point to 0 as we don't draw outside the range
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x = 0;
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}
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// Ensure that the end point of the line is within range
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if (x + no_pixels - dpi->width > 0)
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{
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// If the end point has any pixels outside range
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// cut them off. If there are now no pixels return.
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no_pixels -= x + no_pixels - dpi->width;
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if (no_pixels <= 0)
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return;
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}
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// Get the buffer we are drawing to and move to the first coordinate.
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uint8_t* bits_pointer = dpi->bits + y * (dpi->pitch + dpi->width) + x;
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// Draw the line to the specified colour
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for (; no_pixels > 0; --no_pixels, ++bits_pointer)
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{
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*bits_pointer = colour;
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}
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}
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/**
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* Draws a line on dpi if within dpi boundaries
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* rct2: 0x00684466
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* dpi (edi)
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* x1 (ax)
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* y1 (bx)
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* x2 (cx)
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* y2 (dx)
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* colour (ebp)
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*/
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void gfx_draw_line_software(rct_drawpixelinfo* dpi, int32_t x1, int32_t y1, int32_t x2, int32_t y2, int32_t colour)
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{
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// Check to make sure the line is within the drawing area
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if ((x1 < dpi->x) && (x2 < dpi->x))
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{
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return;
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}
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if ((y1 < dpi->y) && (y2 < dpi->y))
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{
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return;
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}
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if ((x1 > (dpi->x + dpi->width)) && (x2 > (dpi->x + dpi->width)))
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{
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return;
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}
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if ((y1 > (dpi->y + dpi->height)) && (y2 > (dpi->y + dpi->height)))
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{
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return;
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}
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// Bresenham's algorithm
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// If vertical plot points upwards
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int32_t steep = std::abs(y2 - y1) > std::abs(x2 - x1);
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if (steep)
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{
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int32_t temp_y2 = y2;
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int32_t temp_x2 = x2;
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y2 = x1;
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x2 = y1;
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y1 = temp_x2;
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x1 = temp_y2;
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}
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// If line is right to left swap direction
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if (x1 > x2)
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{
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int32_t temp_y2 = y2;
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int32_t temp_x2 = x2;
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y2 = y1;
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x2 = x1;
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y1 = temp_y2;
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x1 = temp_x2;
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}
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int32_t delta_x = x2 - x1;
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int32_t delta_y = std::abs(y2 - y1);
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int32_t error = delta_x / 2;
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int32_t y_step;
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int32_t y = y1;
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// Direction of step
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if (y1 < y2)
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y_step = 1;
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else
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y_step = -1;
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for (int32_t x = x1, x_start = x1, no_pixels = 1; x < x2; ++x, ++no_pixels)
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{
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// Vertical lines are drawn 1 pixel at a time
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if (steep)
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gfx_draw_line_on_buffer(dpi, colour, x, y, 1);
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error -= delta_y;
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if (error < 0)
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{
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// Non vertical lines are drawn with as many pixels in a horizontal line as possible
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if (!steep)
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gfx_draw_line_on_buffer(dpi, colour, y, x_start, no_pixels);
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// Reset non vertical line vars
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x_start = x + 1;
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no_pixels = 1;
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y += y_step;
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error += delta_x;
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}
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// Catch the case of the last line
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if (x + 1 == x2 && !steep)
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{
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gfx_draw_line_on_buffer(dpi, colour, y, x_start, no_pixels);
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}
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}
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}
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