kc3-lang/SDL/src/video/SDL_blit_slow.c

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• Hash : ab0cf42a
  Author :
  Date : 2021-03-04T14:33:56
  

  Software nearest scaling: start at the middle of pixel so that it matches opengl GL_NEAREST mode most of the time

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• src/video/SDL_blit_slow.c

• /*
    Simple DirectMedia Layer
    Copyright (C) 1997-2021 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 "SDL_video.h"
  #include "SDL_blit.h"
  #include "SDL_blit_slow.h"
  
  /* The ONE TRUE BLITTER
   * This puppy has to handle all the unoptimized cases - yes, it's slow.
   */
  void
  SDL_Blit_Slow(SDL_BlitInfo * info)
  {
      const int flags = info->flags;
      const Uint32 modulateR = info->r;
      const Uint32 modulateG = info->g;
      const Uint32 modulateB = info->b;
      const Uint32 modulateA = info->a;
      Uint32 srcpixel;
      Uint32 srcR, srcG, srcB, srcA;
      Uint32 dstpixel;
      Uint32 dstR, dstG, dstB, dstA;
      int srcy, srcx;
      Uint32 posy, posx;
      int incy, incx;
      SDL_PixelFormat *src_fmt = info->src_fmt;
      SDL_PixelFormat *dst_fmt = info->dst_fmt;
      int srcbpp = src_fmt->BytesPerPixel;
      int dstbpp = dst_fmt->BytesPerPixel;
      Uint32 rgbmask = ~src_fmt->Amask;
      Uint32 ckey = info->colorkey & rgbmask;
  
      incy = (info->src_h << 16) / info->dst_h;
      incx = (info->src_w << 16) / info->dst_w;
      posy = incy / 2; /* start at the middle of pixel */
  
      while (info->dst_h--) {
          Uint8 *src = 0;
          Uint8 *dst = info->dst;
          int n = info->dst_w;
          posx = incx / 2; /* start at the middle of pixel */
          srcy = posy >> 16;
          while (n--) {
              srcx = posx >> 16;
              src = (info->src + (srcy * info->src_pitch) + (srcx * srcbpp));
              if (src_fmt->Amask) {
                  DISEMBLE_RGBA(src, srcbpp, src_fmt, srcpixel, srcR, srcG,
                                srcB, srcA);
              } else {
                  DISEMBLE_RGB(src, srcbpp, src_fmt, srcpixel, srcR, srcG,
                               srcB);
                  srcA = 0xFF;
              }
              if (flags & SDL_COPY_COLORKEY) {
                  /* srcpixel isn't set for 24 bpp */
                  if (srcbpp == 3) {
                      srcpixel = (srcR << src_fmt->Rshift) |
                          (srcG << src_fmt->Gshift) | (srcB << src_fmt->Bshift);
                  }
                  if ((srcpixel & rgbmask) == ckey) {
                      posx += incx;
                      dst += dstbpp;
                      continue;
                  }
              }
              if (dst_fmt->Amask) {
                  DISEMBLE_RGBA(dst, dstbpp, dst_fmt, dstpixel, dstR, dstG,
                                dstB, dstA);
              } else {
                  DISEMBLE_RGB(dst, dstbpp, dst_fmt, dstpixel, dstR, dstG,
                               dstB);
                  dstA = 0xFF;
              }
  
              if (flags & SDL_COPY_MODULATE_COLOR) {
                  srcR = (srcR * modulateR) / 255;
                  srcG = (srcG * modulateG) / 255;
                  srcB = (srcB * modulateB) / 255;
              }
              if (flags & SDL_COPY_MODULATE_ALPHA) {
                  srcA = (srcA * modulateA) / 255;
              }
              if (flags & (SDL_COPY_BLEND | SDL_COPY_ADD)) {
                  /* This goes away if we ever use premultiplied alpha */
                  if (srcA < 255) {
                      srcR = (srcR * srcA) / 255;
                      srcG = (srcG * srcA) / 255;
                      srcB = (srcB * srcA) / 255;
                  }
              }
              switch (flags & (SDL_COPY_BLEND | SDL_COPY_ADD | SDL_COPY_MOD | SDL_COPY_MUL)) {
              case 0:
                  dstR = srcR;
                  dstG = srcG;
                  dstB = srcB;
                  dstA = srcA;
                  break;
              case SDL_COPY_BLEND:
                  dstR = srcR + ((255 - srcA) * dstR) / 255;
                  dstG = srcG + ((255 - srcA) * dstG) / 255;
                  dstB = srcB + ((255 - srcA) * dstB) / 255;
                  dstA = srcA + ((255 - srcA) * dstA) / 255;
                  break;
              case SDL_COPY_ADD:
                  dstR = srcR + dstR;
                  if (dstR > 255)
                      dstR = 255;
                  dstG = srcG + dstG;
                  if (dstG > 255)
                      dstG = 255;
                  dstB = srcB + dstB;
                  if (dstB > 255)
                      dstB = 255;
                  break;
              case SDL_COPY_MOD:
                  dstR = (srcR * dstR) / 255;
                  dstG = (srcG * dstG) / 255;
                  dstB = (srcB * dstB) / 255;
                  break;
              case SDL_COPY_MUL:
                  dstR = ((srcR * dstR) + (dstR * (255 - srcA))) / 255;
                  if (dstR > 255)
                      dstR = 255;
                  dstG = ((srcG * dstG) + (dstG * (255 - srcA))) / 255;
                  if (dstG > 255)
                      dstG = 255;
                  dstB = ((srcB * dstB) + (dstB * (255 - srcA))) / 255;
                  if (dstB > 255)
                      dstB = 255;
                  dstA = ((srcA * dstA) + (dstA * (255 - srcA))) / 255;
                  if (dstA > 255)
                      dstA = 255;
                  break;
              }
              if (dst_fmt->Amask) {
                  ASSEMBLE_RGBA(dst, dstbpp, dst_fmt, dstR, dstG, dstB, dstA);
              } else {
                  ASSEMBLE_RGB(dst, dstbpp, dst_fmt, dstR, dstG, dstB);
              }
              posx += incx;
              dst += dstbpp;
          }
          posy += incy;
          info->dst += info->dst_pitch;
      }
  }
  
  /* vi: set ts=4 sw=4 expandtab: */
  

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