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view src/video/SDL_blendrect.c @ 3473:7bdc10624cba

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This is terrible, but the OpenGL standard says that lines are half open, which means that one endpoint is not covered so adjoining lines don't overlap. It also doesn't define which end is open, and indeed Mac OS X and Linux differ. Mac OS X seems to leave the second endpoint open, but Linux uses the right-most endpoint for x major lines and the bottom-most endpoint for y major lines.
author Sam Lantinga <slouken@libsdl.org>
date Sat, 21 Nov 2009 07:14:21 +0000
parents 3a9636c83849
children 0267b8b1595c
line wrap: on
line source

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2009 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Sam Lantinga
    slouken@libsdl.org
*/
#include "SDL_config.h"

#include "SDL_video.h"
#include "SDL_draw.h"

static int
SDL_BlendRect_RGB555(SDL_Surface * dst, SDL_Rect * dstrect, int blendMode,
                     Uint8 r, Uint8 g, Uint8 b, Uint8 a)
{
    unsigned inva = 0xff - a;

    switch (blendMode) {
    case SDL_BLENDMODE_BLEND:
        FILLRECT(Uint16, DRAW_SETPIXEL_BLEND_RGB555);
        break;
    case SDL_BLENDMODE_ADD:
        FILLRECT(Uint16, DRAW_SETPIXEL_ADD_RGB555);
        break;
    case SDL_BLENDMODE_MOD:
        FILLRECT(Uint16, DRAW_SETPIXEL_MOD_RGB555);
        break;
    default:
        FILLRECT(Uint16, DRAW_SETPIXEL_RGB555);
        break;
    }
    return 0;
}

static int
SDL_BlendRect_RGB565(SDL_Surface * dst, SDL_Rect * dstrect, int blendMode,
                     Uint8 r, Uint8 g, Uint8 b, Uint8 a)
{
    unsigned inva = 0xff - a;

    switch (blendMode) {
    case SDL_BLENDMODE_BLEND:
        FILLRECT(Uint16, DRAW_SETPIXEL_BLEND_RGB565);
        break;
    case SDL_BLENDMODE_ADD:
        FILLRECT(Uint16, DRAW_SETPIXEL_ADD_RGB565);
        break;
    case SDL_BLENDMODE_MOD:
        FILLRECT(Uint16, DRAW_SETPIXEL_MOD_RGB565);
        break;
    default:
        FILLRECT(Uint16, DRAW_SETPIXEL_RGB565);
        break;
    }
    return 0;
}

static int
SDL_BlendRect_RGB888(SDL_Surface * dst, SDL_Rect * dstrect, int blendMode,
                     Uint8 r, Uint8 g, Uint8 b, Uint8 a)
{
    unsigned inva = 0xff - a;

    switch (blendMode) {
    case SDL_BLENDMODE_BLEND:
        FILLRECT(Uint32, DRAW_SETPIXEL_BLEND_RGB888);
        break;
    case SDL_BLENDMODE_ADD:
        FILLRECT(Uint32, DRAW_SETPIXEL_ADD_RGB888);
        break;
    case SDL_BLENDMODE_MOD:
        FILLRECT(Uint32, DRAW_SETPIXEL_MOD_RGB888);
        break;
    default:
        FILLRECT(Uint32, DRAW_SETPIXEL_RGB888);
        break;
    }
    return 0;
}

static int
SDL_BlendRect_ARGB8888(SDL_Surface * dst, SDL_Rect * dstrect, int blendMode,
                       Uint8 r, Uint8 g, Uint8 b, Uint8 a)
{
    unsigned inva = 0xff - a;

    switch (blendMode) {
    case SDL_BLENDMODE_BLEND:
        FILLRECT(Uint32, DRAW_SETPIXEL_BLEND_ARGB8888);
        break;
    case SDL_BLENDMODE_ADD:
        FILLRECT(Uint32, DRAW_SETPIXEL_ADD_ARGB8888);
        break;
    case SDL_BLENDMODE_MOD:
        FILLRECT(Uint32, DRAW_SETPIXEL_MOD_ARGB8888);
        break;
    default:
        FILLRECT(Uint32, DRAW_SETPIXEL_ARGB8888);
        break;
    }
    return 0;
}

static int
SDL_BlendRect_RGB(SDL_Surface * dst, SDL_Rect * dstrect, int blendMode,
                  Uint8 r, Uint8 g, Uint8 b, Uint8 a)
{
    SDL_PixelFormat *fmt = dst->format;
    unsigned inva = 0xff - a;

    switch (fmt->BytesPerPixel) {
    case 2:
        switch (blendMode) {
        case SDL_BLENDMODE_BLEND:
            FILLRECT(Uint16, DRAW_SETPIXEL_BLEND_RGB);
            break;
        case SDL_BLENDMODE_ADD:
            FILLRECT(Uint16, DRAW_SETPIXEL_ADD_RGB);
            break;
        case SDL_BLENDMODE_MOD:
            FILLRECT(Uint16, DRAW_SETPIXEL_MOD_RGB);
            break;
        default:
            FILLRECT(Uint16, DRAW_SETPIXEL_RGB);
            break;
        }
        return 0;
    case 4:
        switch (blendMode) {
        case SDL_BLENDMODE_BLEND:
            FILLRECT(Uint32, DRAW_SETPIXEL_BLEND_RGB);
            break;
        case SDL_BLENDMODE_ADD:
            FILLRECT(Uint32, DRAW_SETPIXEL_ADD_RGB);
            break;
        case SDL_BLENDMODE_MOD:
            FILLRECT(Uint32, DRAW_SETPIXEL_MOD_RGB);
            break;
        default:
            FILLRECT(Uint32, DRAW_SETPIXEL_RGB);
            break;
        }
        return 0;
    default:
        SDL_Unsupported();
        return -1;
    }
}

static int
SDL_BlendRect_RGBA(SDL_Surface * dst, SDL_Rect * dstrect, int blendMode,
                   Uint8 r, Uint8 g, Uint8 b, Uint8 a)
{
    SDL_PixelFormat *fmt = dst->format;
    unsigned inva = 0xff - a;

    switch (fmt->BytesPerPixel) {
    case 4:
        switch (blendMode) {
        case SDL_BLENDMODE_BLEND:
            FILLRECT(Uint32, DRAW_SETPIXEL_BLEND_RGBA);
            break;
        case SDL_BLENDMODE_ADD:
            FILLRECT(Uint32, DRAW_SETPIXEL_ADD_RGBA);
            break;
        case SDL_BLENDMODE_MOD:
            FILLRECT(Uint32, DRAW_SETPIXEL_MOD_RGBA);
            break;
        default:
            FILLRECT(Uint32, DRAW_SETPIXEL_RGBA);
            break;
        }
        return 0;
    default:
        SDL_Unsupported();
        return -1;
    }
}

int
SDL_BlendRect(SDL_Surface * dst, SDL_Rect * dstrect, int blendMode, Uint8 r,
              Uint8 g, Uint8 b, Uint8 a)
{
    SDL_PixelFormat *fmt = dst->format;

    /* This function doesn't work on surfaces < 8 bpp */
    if (fmt->BitsPerPixel < 8) {
        SDL_SetError("SDL_BlendRect(): Unsupported surface format");
        return (-1);
    }

    /* If 'dstrect' == NULL, then fill the whole surface */
    if (dstrect) {
        /* Perform clipping */
        if (!SDL_IntersectRect(dstrect, &dst->clip_rect, dstrect)) {
            return (0);
        }
    } else {
        dstrect = &dst->clip_rect;
    }

    if ((blendMode == SDL_BLENDMODE_BLEND)
        || (blendMode == SDL_BLENDMODE_ADD)) {
        r = DRAW_MUL(r, a);
        g = DRAW_MUL(g, a);
        b = DRAW_MUL(b, a);
    }

    switch (fmt->BitsPerPixel) {
    case 15:
        switch (fmt->Rmask) {
        case 0x7C00:
            return SDL_BlendRect_RGB555(dst, dstrect, blendMode, r, g, b, a);
        }
        break;
    case 16:
        switch (fmt->Rmask) {
        case 0xF800:
            return SDL_BlendRect_RGB565(dst, dstrect, blendMode, r, g, b, a);
        }
        break;
    case 32:
        switch (fmt->Rmask) {
        case 0x00FF0000:
            if (!fmt->Amask) {
                return SDL_BlendRect_RGB888(dst, dstrect, blendMode, r, g, b,
                                            a);
            } else {
                return SDL_BlendRect_ARGB8888(dst, dstrect, blendMode, r, g,
                                              b, a);
            }
            break;
        }
    default:
        break;
    }

    if (!fmt->Amask) {
        return SDL_BlendRect_RGB(dst, dstrect, blendMode, r, g, b, a);
    } else {
        return SDL_BlendRect_RGBA(dst, dstrect, blendMode, r, g, b, a);
    }
}

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