码迷，mamicode.com
首页 > 其他好文 > 详细

SDL2源代码分析6：复制到渲染器（SDL_RenderCopy()）

时间：2014-11-08 02:11:47      阅读：346      评论：0      收藏：0      [点我收藏+]

标签：sdl   direct3d   opengl   gdi   渲染   

上一篇文章分析了SDL更新纹理像素数据的函数SDL_UpdateTexture()。这篇文章继续分析SDL的源代码。本文分析SDL纹理复制到渲染目标的函数SDL_RenderCopy()。
bubuko.com,布布扣

 


SDL播放视频的代码流程如下所示。
初始化: 
SDL_Init(): 初始化SDL。 
SDL_CreateWindow(): 创建窗口（Window）。 
SDL_CreateRenderer(): 基于窗口创建渲染器（Render）。 
SDL_CreateTexture(): 创建纹理（Texture）。 
循环渲染数据: 
SDL_UpdateTexture(): 设置纹理的数据。 
SDL_RenderCopy(): 纹理复制给渲染器。 
SDL_RenderPresent(): 显示。
上篇文章分析了该流程中的第5个函数SDL_UpdateTexture()。本文继续分析该流程中的第6个函数SDL_RenderCopy()。


SDL_RenderCopy()

函数简介

SDL使用SDL_RenderCopy()将纹理数据复制给渲染目标。SDL_RenderCopy()定义如下。

int SDLCALL SDL_RenderCopy(SDL_Renderer * renderer,
                                           SDL_Texture * texture,
                                           const SDL_Rect * srcrect,
                                           const SDL_Rect * dstrect);

参数的含义如下。
renderer：渲染目标。
texture：输入纹理。
srcrect：选择输入纹理的一块矩形区域作为输入。设置为NULL的时候整个纹理作为输入。
dstrect：选择渲染目标的一块矩形区域作为输出。设置为NULL的时候整个渲染目标作为输出。


成功的话返回0，失败的话返回-1。


函数调用关系图

SDL_RenderCopy()关键函数的调用关系可以用下图表示。

bubuko.com,布布扣

上面的图片不太清晰，更清晰的图片上传到了相册里面：

http://my.csdn.net/leixiaohua1020/album/detail/1793911

把相册里面的图片保存下来就可以得到清晰的图片了。


源代码分析

SDL_RenderCopy()的源代码位于render\SDL_render.c中，如下所示。

int SDL_RenderCopy(SDL_Renderer * renderer, SDL_Texture * texture,
               const SDL_Rect * srcrect, const SDL_Rect * dstrect)
{
    SDL_Rect real_srcrect = { 0, 0, 0, 0 };
    SDL_Rect real_dstrect = { 0, 0, 0, 0 };
    SDL_FRect frect;


    CHECK_RENDERER_MAGIC(renderer, -1);
    CHECK_TEXTURE_MAGIC(texture, -1);


    if (renderer != texture->renderer) {
        return SDL_SetError("Texture was not created with this renderer");
    }


    real_srcrect.x = 0;
    real_srcrect.y = 0;
    real_srcrect.w = texture->w;
    real_srcrect.h = texture->h;
    if (srcrect) {
        if (!SDL_IntersectRect(srcrect, &real_srcrect, &real_srcrect)) {
            return 0;
        }
    }


    SDL_RenderGetViewport(renderer, &real_dstrect);
    real_dstrect.x = 0;
    real_dstrect.y = 0;
    if (dstrect) {
        if (!SDL_HasIntersection(dstrect, &real_dstrect)) {
            return 0;
        }
        real_dstrect = *dstrect;
    }


    if (texture->native) {
        texture = texture->native;
    }


    /* Don‘t draw while we‘re hidden */
    if (renderer->hidden) {
        return 0;
    }


    frect.x = real_dstrect.x * renderer->scale.x;
    frect.y = real_dstrect.y * renderer->scale.y;
    frect.w = real_dstrect.w * renderer->scale.x;
    frect.h = real_dstrect.h * renderer->scale.y;


    return renderer->RenderCopy(renderer, texture, &real_srcrect, &frect);
}

从源代码中可以看出，SDL_RenderCopy()的大致流程如下。

1. 检查输入参数的合理性。
2. 调用SDL_Render的RenderCopy ()方法复制纹理到渲染目标。这一步是整个函数的核心。
下面我们详细看一下几种不同的渲染器的RenderCopy()的方法。

1. Direct3D

Direct3D 渲染器中对应RenderCopy()的函数是D3D_RenderCopy()，它的源代码如下所示（位于render\direct3d\SDL_render_d3d.c）。
static int D3D_RenderCopy(SDL_Renderer * renderer, SDL_Texture * texture,
               const SDL_Rect * srcrect, const SDL_FRect * dstrect)
{
    D3D_RenderData *data = (D3D_RenderData *) renderer->driverdata;
    D3D_TextureData *texturedata;
    LPDIRECT3DPIXELSHADER9 shader = NULL;
    float minx, miny, maxx, maxy;
    float minu, maxu, minv, maxv;
    DWORD color;
    Vertex vertices[4];
    HRESULT result;


    if (D3D_ActivateRenderer(renderer) < 0) {
        return -1;
    }


    texturedata = (D3D_TextureData *)texture->driverdata;
    if (!texturedata) {
        SDL_SetError("Texture is not currently available");
        return -1;
    }


    minx = dstrect->x - 0.5f;
    miny = dstrect->y - 0.5f;
    maxx = dstrect->x + dstrect->w - 0.5f;
    maxy = dstrect->y + dstrect->h - 0.5f;


    minu = (float) srcrect->x / texture->w;
    maxu = (float) (srcrect->x + srcrect->w) / texture->w;
    minv = (float) srcrect->y / texture->h;
    maxv = (float) (srcrect->y + srcrect->h) / texture->h;


    color = D3DCOLOR_ARGB(texture->a, texture->r, texture->g, texture->b);


    vertices[0].x = minx;
    vertices[0].y = miny;
    vertices[0].z = 0.0f;
    vertices[0].color = color;
    vertices[0].u = minu;
    vertices[0].v = minv;


    vertices[1].x = maxx;
    vertices[1].y = miny;
    vertices[1].z = 0.0f;
    vertices[1].color = color;
    vertices[1].u = maxu;
    vertices[1].v = minv;


    vertices[2].x = maxx;
    vertices[2].y = maxy;
    vertices[2].z = 0.0f;
    vertices[2].color = color;
    vertices[2].u = maxu;
    vertices[2].v = maxv;


    vertices[3].x = minx;
    vertices[3].y = maxy;
    vertices[3].z = 0.0f;
    vertices[3].color = color;
    vertices[3].u = minu;
    vertices[3].v = maxv;


    D3D_SetBlendMode(data, texture->blendMode);


    D3D_UpdateTextureScaleMode(data, texturedata, 0);


    result =
        IDirect3DDevice9_SetTexture(data->device, 0, (IDirect3DBaseTexture9 *)
                                    texturedata->texture);
    if (FAILED(result)) {
        return D3D_SetError("SetTexture()", result);
    }


    if (texturedata->yuv) {
        shader = data->ps_yuv;


        D3D_UpdateTextureScaleMode(data, texturedata, 1);
        D3D_UpdateTextureScaleMode(data, texturedata, 2);


        result =
            IDirect3DDevice9_SetTexture(data->device, 1, (IDirect3DBaseTexture9 *)
                                        texturedata->utexture);
        if (FAILED(result)) {
            return D3D_SetError("SetTexture()", result);
        }


        result =
            IDirect3DDevice9_SetTexture(data->device, 2, (IDirect3DBaseTexture9 *)
                                        texturedata->vtexture);
        if (FAILED(result)) {
            return D3D_SetError("SetTexture()", result);
        }
    }


    if (shader) {
        result = IDirect3DDevice9_SetPixelShader(data->device, shader);
        if (FAILED(result)) {
            return D3D_SetError("SetShader()", result);
        }
    }
    result =
        IDirect3DDevice9_DrawPrimitiveUP(data->device, D3DPT_TRIANGLEFAN, 2,
                                         vertices, sizeof(*vertices));
    if (FAILED(result)) {
        return D3D_SetError("DrawPrimitiveUP()", result);
    }
    if (shader) {
        result = IDirect3DDevice9_SetPixelShader(data->device, NULL);
        if (FAILED(result)) {
            return D3D_SetError("SetShader()", result);
        }
    }
    return 0;
}

从代码中可以看出，D3D_RenderCopy()函数按照执行的顺序调用了如下函数：

D3D_ActivateRenderer()：激活渲染器。其内部使用Direct3D的API函数IDirect3DDevice9_BeginScene()开始一个D3D的场景。
D3D_SetBlendMode()：设置渲染器状态。其内部使用Direct3D的API函数IDirect3DDevice9_SetRenderState()设置渲染器的状态。
D3D_UpdateTextureScaleMode()：设置纹理采样方式。其内部调用使用Direct3D的API函数IDirect3DDevice9_SetSamplerState()设置D3D的纹理采样方式。
IDirect3DDevice9_SetTexture()：Direct3D的API，用于设置当前启用的纹理。
IDirect3DDevice9_SetPixelShader()：Direct3D的API，用于设置使用的像素着色器。

IDirect3DDevice9_DrawPrimitiveUP()：Direct3D的API，用于渲染。

上述几个函数中，前3个函数是SDL中的函数，后3个函数是Direct3D的API。在此附上前三个函数的代码。

D3D_ActivateRenderer()：激活渲染器。

static int D3D_ActivateRenderer(SDL_Renderer * renderer)
{
    D3D_RenderData *data = (D3D_RenderData *) renderer->driverdata;
    HRESULT result;


    if (data->updateSize) {
        SDL_Window *window = renderer->window;
        int w, h;


        SDL_GetWindowSize(window, &w, &h);
        data->pparams.BackBufferWidth = w;
        data->pparams.BackBufferHeight = h;
        if (SDL_GetWindowFlags(window) & SDL_WINDOW_FULLSCREEN) {
            data->pparams.BackBufferFormat =
                PixelFormatToD3DFMT(SDL_GetWindowPixelFormat(window));
        } else {
            data->pparams.BackBufferFormat = D3DFMT_UNKNOWN;
        }
        if (D3D_Reset(renderer) < 0) {
            return -1;
        }


        data->updateSize = SDL_FALSE;
    }
    if (data->beginScene) {
        result = IDirect3DDevice9_BeginScene(data->device);
        if (result == D3DERR_DEVICELOST) {
            if (D3D_Reset(renderer) < 0) {
                return -1;
            }
            result = IDirect3DDevice9_BeginScene(data->device);
        }
        if (FAILED(result)) {
            return D3D_SetError("BeginScene()", result);
        }
        data->beginScene = SDL_FALSE;
    }
    return 0;
}


D3D_SetBlendMode()：设置渲染器状态。

static void D3D_SetBlendMode(D3D_RenderData * data, int blendMode)
{
    switch (blendMode) {
    case SDL_BLENDMODE_NONE:
        IDirect3DDevice9_SetRenderState(data->device, D3DRS_ALPHABLENDENABLE,
                                        FALSE);
        break;
    case SDL_BLENDMODE_BLEND:
        IDirect3DDevice9_SetRenderState(data->device, D3DRS_ALPHABLENDENABLE,
                                        TRUE);
        IDirect3DDevice9_SetRenderState(data->device, D3DRS_SRCBLEND,
                                        D3DBLEND_SRCALPHA);
        IDirect3DDevice9_SetRenderState(data->device, D3DRS_DESTBLEND,
                                        D3DBLEND_INVSRCALPHA);
        if (data->enableSeparateAlphaBlend) {
            IDirect3DDevice9_SetRenderState(data->device, D3DRS_SRCBLENDALPHA,
                                            D3DBLEND_ONE);
            IDirect3DDevice9_SetRenderState(data->device, D3DRS_DESTBLENDALPHA,
                                            D3DBLEND_INVSRCALPHA);
        }
        break;
    case SDL_BLENDMODE_ADD:
        IDirect3DDevice9_SetRenderState(data->device, D3DRS_ALPHABLENDENABLE,
                                        TRUE);
        IDirect3DDevice9_SetRenderState(data->device, D3DRS_SRCBLEND,
                                        D3DBLEND_SRCALPHA);
        IDirect3DDevice9_SetRenderState(data->device, D3DRS_DESTBLEND,
                                        D3DBLEND_ONE);
        if (data->enableSeparateAlphaBlend) {
            IDirect3DDevice9_SetRenderState(data->device, D3DRS_SRCBLENDALPHA,
                                            D3DBLEND_ZERO);
            IDirect3DDevice9_SetRenderState(data->device, D3DRS_DESTBLENDALPHA,
                                            D3DBLEND_ONE);
        }
        break;
    case SDL_BLENDMODE_MOD:
        IDirect3DDevice9_SetRenderState(data->device, D3DRS_ALPHABLENDENABLE,
                                        TRUE);
        IDirect3DDevice9_SetRenderState(data->device, D3DRS_SRCBLEND,
                                        D3DBLEND_ZERO);
        IDirect3DDevice9_SetRenderState(data->device, D3DRS_DESTBLEND,
                                        D3DBLEND_SRCCOLOR);
        if (data->enableSeparateAlphaBlend) {
            IDirect3DDevice9_SetRenderState(data->device, D3DRS_SRCBLENDALPHA,
                                            D3DBLEND_ZERO);
            IDirect3DDevice9_SetRenderState(data->device, D3DRS_DESTBLENDALPHA,
                                            D3DBLEND_ONE);
        }
        break;
    }
}


D3D_UpdateTextureScaleMode()：设置纹理采样方式。

static void D3D_UpdateTextureScaleMode(D3D_RenderData *data, D3D_TextureData *texturedata, unsigned index)
{
    if (texturedata->scaleMode != data->scaleMode[index]) {
        IDirect3DDevice9_SetSamplerState(data->device, index, D3DSAMP_MINFILTER,
                                         texturedata->scaleMode);
        IDirect3DDevice9_SetSamplerState(data->device, index, D3DSAMP_MAGFILTER,
                                         texturedata->scaleMode);
        data->scaleMode[index] = texturedata->scaleMode;
    }
}

2. OpenGL

OpenGL渲染器中对应RenderCopy()的函数是GL_RenderCopy()，它的源代码如下所示（位于render\opengl\SDL_render_gl.c）。

static int GL_RenderCopy(SDL_Renderer * renderer, SDL_Texture * texture,
              const SDL_Rect * srcrect, const SDL_FRect * dstrect)
{
    GL_RenderData *data = (GL_RenderData *) renderer->driverdata;
    GL_TextureData *texturedata = (GL_TextureData *) texture->driverdata;
    GLfloat minx, miny, maxx, maxy;
    GLfloat minu, maxu, minv, maxv;


    GL_ActivateRenderer(renderer);


    data->glEnable(texturedata->type);
    if (texturedata->yuv) {
        data->glActiveTextureARB(GL_TEXTURE2_ARB);
        data->glBindTexture(texturedata->type, texturedata->vtexture);


        data->glActiveTextureARB(GL_TEXTURE1_ARB);
        data->glBindTexture(texturedata->type, texturedata->utexture);


        data->glActiveTextureARB(GL_TEXTURE0_ARB);
    }
    data->glBindTexture(texturedata->type, texturedata->texture);


    if (texture->modMode) {
        GL_SetColor(data, texture->r, texture->g, texture->b, texture->a);
    } else {
        GL_SetColor(data, 255, 255, 255, 255);
    }


    GL_SetBlendMode(data, texture->blendMode);


    if (texturedata->yuv) {
        GL_SetShader(data, SHADER_YV12);
    } else {
        GL_SetShader(data, SHADER_RGB);
    }


    minx = dstrect->x;
    miny = dstrect->y;
    maxx = dstrect->x + dstrect->w;
    maxy = dstrect->y + dstrect->h;


    minu = (GLfloat) srcrect->x / texture->w;
    minu *= texturedata->texw;
    maxu = (GLfloat) (srcrect->x + srcrect->w) / texture->w;
    maxu *= texturedata->texw;
    minv = (GLfloat) srcrect->y / texture->h;
    minv *= texturedata->texh;
    maxv = (GLfloat) (srcrect->y + srcrect->h) / texture->h;
    maxv *= texturedata->texh;


    data->glBegin(GL_TRIANGLE_STRIP);
    data->glTexCoord2f(minu, minv);
    data->glVertex2f(minx, miny);
    data->glTexCoord2f(maxu, minv);
    data->glVertex2f(maxx, miny);
    data->glTexCoord2f(minu, maxv);
    data->glVertex2f(minx, maxy);
    data->glTexCoord2f(maxu, maxv);
    data->glVertex2f(maxx, maxy);
    data->glEnd();


    data->glDisable(texturedata->type);


    return GL_CheckError("", renderer);
}

从代码中可以看出，GL_RenderCopy()函数调用了OpenGL的API函数glActiveTexture()，glBindTexture()创建了一个纹理。并且使用GL_SetBlendMode()，GL_SetShader()设置了有关的一些参数。

有一点需要注意，在OpenGL渲染器中，如果输入像素格式是YUV，就会使用3个纹理。

3. Software

Software渲染器中对应RenderCopy()的函数是SW_RenderCopy()，它的源代码如下所示（位于render\software\SDL_render_sw.c）。

static int SW_RenderCopy(SDL_Renderer * renderer, SDL_Texture * texture,
              const SDL_Rect * srcrect, const SDL_FRect * dstrect)
{
    SDL_Surface *surface = SW_ActivateRenderer(renderer);
    SDL_Surface *src = (SDL_Surface *) texture->driverdata;
    SDL_Rect final_rect;


    if (!surface) {
        return -1;
    }


    if (renderer->viewport.x || renderer->viewport.y) {
        final_rect.x = (int)(renderer->viewport.x + dstrect->x);
        final_rect.y = (int)(renderer->viewport.y + dstrect->y);
    } else {
        final_rect.x = (int)dstrect->x;
        final_rect.y = (int)dstrect->y;
    }
    final_rect.w = (int)dstrect->w;
    final_rect.h = (int)dstrect->h;


    if ( srcrect->w == final_rect.w && srcrect->h == final_rect.h ) {
        return SDL_BlitSurface(src, srcrect, surface, &final_rect);
    } else {
        return SDL_BlitScaled(src, srcrect, surface, &final_rect);
    }
}

该函数的源代码还没有详细分析。




SDL2源代码分析6：复制到渲染器（SDL_RenderCopy()）

标签：sdl   direct3d   opengl   gdi   渲染   

原文地址：http://blog.csdn.net/leixiaohua1020/article/details/40895593
踩
(0)
赞
(0)
   
举报
评论 一句话评论（0）
登录后才能评论！
分享档案
更多>
2021年07月29日 (22)
2021年07月28日 (40)
2021年07月27日 (32)
2021年07月26日 (79)
2021年07月23日 (29)
2021年07月22日 (30)
2021年07月21日 (42)
2021年07月20日 (16)
2021年07月19日 (90)
2021年07月16日 (35)
周排行
mamicode.com排行更多图片
更多
友情链接
兰亭集智   国之画   百度统计   站长统计   阿里云   chrome插件   新版天听网
关于我们 - 联系我们 - 留言反馈
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码！