如何通过 opengl 混合 RGB 和 BGRA 原始图像？

Question

我是 OpenGL 的新手

正在尝试混合 RGB 和 BGRA 原始图像。

RGB 为背景图像
RGBA 为前景图像

下面的源只得到输出，"osd_raw"图像。混合没有发生。

在下面的代码中加载 2 个原始图像。创建 2 个纹理并与之绑定。使用 glBlendFunc 进行混合。输出没有混合。

请告诉我哪里出错了。

void display()
{

    GLuint texture[2];
    int width = 960;
    int height = 540;
    unsigned char *osd_raw = loadFile("./osd.raw");
    unsigned char *video_raw = loadFile("./video.raw");

    glClearColor(0.1, 0.1, 0.1, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);

    glEnable(GL_TEXTURE_2D);
    glGenTextures(2, texture);

    glEnable( GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    glBindTexture(GL_TEXTURE_2D, texture[0]);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, video_raw);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);

    glBindTexture(GL_TEXTURE_2D, texture[1]);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_BGRA, GL_UNSIGNED_BYTE, osd_raw);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);

    glBegin(GL_QUADS);
    glTexCoord2f(0, 0);
    glVertex3f(-1, -1, 0);
    glTexCoord2f(0, 1);
    glVertex3f(-1, 1, 0);
    glTexCoord2f(1, 1);
    glVertex3f(1, 1, 0);
    glTexCoord2f(1, 0);
    glVertex3f(1, -1, 0);
    glEnd();

    glFlush();
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA);

    glutInitWindowSize(960, 540);
    glutInitWindowPosition(0, 0);
    glutCreateWindow("glut test");

    glutDisplayFunc(display);
    glutMainLoop();
    return 0;
}

Answer 1

首先，请注意使用 glBegin/glEnd 序列绘图已被弃用 10 多年了。阅读 Fixed Function Pipeline and see Vertex Specification 了解最先进的渲染方式。

如果要混合 2 个纹理，则必须绑定第一个纹理并使用适当的纹理坐标属性集绘制四边形。之后你必须绑定第二个纹理并再次绘制四边形，启用混合（参见Blending）：

glDisable( GL_BLEND);

glBindTexture(GL_TEXTURE_2D, texture[0]);
glBegin(GL_QUADS);
glTexCoord2f(0, 0);
glVertex3f(-1, -1, 0);
glTexCoord2f(0, 1);
glVertex3f(-1, 1, 0);
glTexCoord2f(1, 1);
glVertex3f(1, 1, 0);
glTexCoord2f(1, 0);
glVertex3f(1, -1, 0);
glEnd();

glEnable( GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

glBindTexture(GL_TEXTURE_2D, texture[1]);
glBegin(GL_QUADS);
glTexCoord2f(0, 0);
glVertex3f(-1, -1, 0);
glTexCoord2f(0, 1);
glVertex3f(-1, 1, 0);
glTexCoord2f(1, 1);
glVertex3f(1, 1, 0);
glTexCoord2f(1, 0);
glVertex3f(1, -1, 0);
glEnd();

进一步注意，Depth Test 必须被禁用或设置为例如GL_LEQUAL，绘制第二个四边形时。否则第二个四边形将被深度测试丢弃。

既然混合函数是glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);，当然第二个textue的一些alpha通道必须小于1.0。

Answer 2

根据Rabbid76，修改后的&以下是参考的工作源。

 void display()
    {
        GLuint texture[2];
        int width = 960;
        int height = 540;
        unsigned char *osd_raw = loadFile("./osd.raw");
        unsigned char *video_raw = loadFile("./video.raw");

        glClearColor(0.1, 0.1, 0.1, 0.0);
        glClear(GL_COLOR_BUFFER_BIT);

        glEnable(GL_TEXTURE_2D);
        glGenTextures(2, texture);

        glDisable(GL_BLEND);

        glBindTexture(GL_TEXTURE_2D, texture[0]);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, video_raw);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

        glBegin(GL_QUADS);
        glTexCoord2f(0, 0);
        glVertex3f(-1, -1, 0);
        glTexCoord2f(0, 1);
        glVertex3f(-1, 1, 0);
        glTexCoord2f(1, 1);
        glVertex3f(1, 1, 0);
        glTexCoord2f(1, 0);
        glVertex3f(1, -1, 0);
        glEnd();

        glEnable( GL_BLEND);
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

        glBindTexture(GL_TEXTURE_2D, texture[1]);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_BGRA, GL_UNSIGNED_BYTE, osd_raw);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

        glBegin(GL_QUADS);
        glTexCoord2f(0, 0);
        glVertex3f(-1, -1, 0);
        glTexCoord2f(0, 1);
        glVertex3f(-1, 1, 0);
        glTexCoord2f(1, 1);
        glVertex3f(1, 1, 0);
        glTexCoord2f(1, 0);
        glVertex3f(1, -1, 0);
        glEnd();

        glFlush();
    }

如何通过 opengl 混合 RGB 和 BGRA 原始图像？

How to blend RGB & BGRA raw images by opengl?

opengl

blending

freeglut