src/render/ngage/SDL_render_ops.cpp

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2025 Sam Lantinga <slouken@libsdl.org>

  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.
*/
#include "SDL_internal.h"

#include <3dtypes.h>
#include "SDL_render_ops.hpp"

void ApplyColorMod(void *dest, void *source, int pitch, int width, int height, SDL_FColor color)
{
    TUint16 *src_pixels = static_cast<TUint16 *>(source);
    TUint16 *dst_pixels = static_cast<TUint16 *>(dest);

    TFixed rf = Real2Fix(color.r);
    TFixed gf = Real2Fix(color.g);
    TFixed bf = Real2Fix(color.b);

    for (int y = 0; y < height; ++y)
    {
        for (int x = 0; x < width; ++x)
        {
            TUint16 pixel = src_pixels[y * pitch / 2 + x];
            TUint8 r = (pixel & 0xF800) >> 8;
            TUint8 g = (pixel & 0x07E0) >> 3;
            TUint8 b = (pixel & 0x001F) << 3;
            r = FixMul(r, rf);
            g = FixMul(g, gf);
            b = FixMul(b, bf);
            dst_pixels[y * pitch / 2 + x] = (r << 8) | (g << 3) | (b >> 3);
        }
    }
}

void ApplyFlip(void *dest, void *source, int pitch, int width, int height, SDL_FlipMode flip)
{
    TUint16 *src_pixels = static_cast<TUint16 *>(source);
    TUint16 *dst_pixels = static_cast<TUint16 *>(dest);

    for (int y = 0; y < height; ++y)
    {
        for (int x = 0; x < width; ++x)
        {
            int src_x = x;
            int src_y = y;

            if (flip & SDL_FLIP_HORIZONTAL)
            {
                src_x = width - 1 - x;
            }

            if (flip & SDL_FLIP_VERTICAL)
            {
                src_y = height - 1 - y;
            }

            dst_pixels[y * pitch / 2 + x] = src_pixels[src_y * pitch / 2 + src_x];
        }
    }
}

void ApplyRotation(void *dest, void *source, int pitch, int width, int height, TFixed center_x, TFixed center_y, TFixed angle)
{
    TUint16 *src_pixels = static_cast<TUint16 *>(source);
    TUint16 *dst_pixels = static_cast<TUint16 *>(dest);

    TFixed cos_angle = 0;
    TFixed sin_angle = 0;

    if (angle != 0)
    {
        FixSinCos(angle, sin_angle, cos_angle);
    }

    for (int y = 0; y < height; ++y)
    {
        for (int x = 0; x < width; ++x)
        {
            // Translate point to origin.
            TFixed translated_x = Int2Fix(x) - center_x;
            TFixed translated_y = Int2Fix(y) - center_y;

            // Rotate point (clockwise).
            TFixed rotated_x = FixMul(translated_x, cos_angle) + FixMul(translated_y, sin_angle);
            TFixed rotated_y = FixMul(translated_y, cos_angle) - FixMul(translated_x, sin_angle);

            // Translate point back.
            int final_x = Fix2Int(rotated_x + center_x);
            int final_y = Fix2Int(rotated_y + center_y);

            // Check bounds.
            if (final_x >= 0 && final_x < width && final_y >= 0 && final_y < height)
            {
                dst_pixels[y * pitch / 2 + x] = src_pixels[final_y * pitch / 2 + final_x];
            }
            else
            {
                dst_pixels[y * pitch / 2 + x] = 0;
            }
        }
    }
}

void ApplyScale(void *dest, void *source, int pitch, int width, int height, TFixed center_x, TFixed center_y, TFixed scale_x, TFixed scale_y)
{
    TUint16 *src_pixels = static_cast<TUint16 *>(source);
    TUint16 *dst_pixels = static_cast<TUint16 *>(dest);

    for (int y = 0; y < height; ++y)
    {
        for (int x = 0; x < width; ++x)
        {
            // Translate point to origin.
            TFixed translated_x = Int2Fix(x) - center_x;
            TFixed translated_y = Int2Fix(y) - center_y;

            // Scale point.
            TFixed scaled_x = FixDiv(translated_x, scale_x);
            TFixed scaled_y = FixDiv(translated_y, scale_y);

            // Translate point back.
            int final_x = Fix2Int(scaled_x + center_x);
            int final_y = Fix2Int(scaled_y + center_y);

            // Check bounds.
            if (final_x >= 0 && final_x < width && final_y >= 0 && final_y < height)
            {
                dst_pixels[y * pitch / 2 + x] = src_pixels[final_y * pitch / 2 + final_x];
            }
            else
            {
                dst_pixels[y * pitch / 2 + x] = 0;
            }
        }
    }
}