Question

我正在尝试缩放图像而不使用太长的函数gluScaleImage（并且没有在我的项目中实现包含“glh”lib（使用glhScaleImage））。我看了this advice：

如果这只是显示各种尺寸的图像，为什么不创建纹理四边形和将其缩放到要求的大小？纹理总是可以是相同的大小。

这就是我尝试使用以下代码：结果是我看到红色写得很好“BACK”，但是看不到“在glflush之前”并且背景有一种奇怪的颜色（有时是紫色，有时是绿色的（关于绿色问题，我怀疑它是错误的初始化）显卡）） =＆GT;任何人都可以告诉我使用glReadPixels获得的缓冲区纹理有什么问题？ =＆GT;还是有另一种解决方案？（我希望修改此代码而不是其他解决方案（framebuffer，...））。

// ---
glColor4ub(255,0,0,200);
myPrintingFunction(200,200,"before glFlush");   
glFlush();

// Unload Bytes
if (mBuffer != NULL)
{
    delete[] mBuffer;
    mBuffer = NULL;
}

// Load Bytes from current window
mBuffer = new GLubyte[ClientWidth * ClientHeight * 4];
glReadBuffer(GL_BACK);
glReadPixels(0, 0, ClientWidth, ClientHeight, GL_BGRA, GL_UNSIGNED_BYTE, mBuffer);

SwapBuffers(ghDC);    

// Unload TextureId
if (mTextureId != 0)
{
    glDeleteTextures(1, &mTextureId);
    mTextureId = 0;
}

// Load TextureId
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glGenTextures(1, &mTextureId);
glBindTexture(GL_TEXTURE_2D, mTextureId);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_BGRA, ClientWidth, ClientHeight, 0, GL_BGRA, GL_UNSIGNED_BYTE, mBuffer);

// ---
glViewport(-mBufferWidth, -mBufferHeight, mBufferWidth * 2, mBufferHeight * 2);

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(double(-mBufferWidth), double(mBufferWidth), double(-mBufferHeight), double(mBufferHeight), 1000.0, 100000.0);

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

glTranslatef(0.0, 0.0, -50000.0);

glClearColor(0,0,0,1);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glEnable(GL_TEXTURE_2D);

glBindTexture(GL_TEXTURE_2D, mTextureId);
mxIncrust0 = 0.0;
myIncrust0 = 0.0;
mxIncrust1 = mBufferWidth;
myIncrust1 = mBufferHeight;
glBegin(GL_QUADS);
    glColor4ub((unsigned char)255,(unsigned char)255,(unsigned char)255,(unsigned char)255);
    glTexCoord2d(0.0, 0.0);
    glVertex2d(mxIncrust0, myIncrust0);
    glTexCoord2d(0.0, 1.0);
    glVertex2d(mxIncrust0, myIncrust1);
    glTexCoord2d(1.0,1.0);
    glVertex2d(mxIncrust1, myIncrust1);
    glTexCoord2d(1.0,0.0);
    glVertex2d(mxIncrust1, myIncrust0);
glEnd();

glDisable(GL_TEXTURE_2D);  

glColor4ub(255,0,0,200);
myPrintingFunction(100,100,"BACK");                                        

glFlush();

if (mBufferPlayout != NULL)
{
    delete[] mBufferPlayout;
    mBufferPlayout = NULL;
}
mBufferPlayout = new GLubyte [mBufferWidth * mBufferHeight * 4];

glReadBuffer(GL_BACK);
glReadPixels(0, 0, mBufferWidth, mBufferHeight, GL_BGRA, GL_UNSIGNED_BYTE, mBufferPlayout);

// then I pass this mBufferPlayout to a graphic card (capture card in output in fact)

Answer 1

好的我发现了错误（glGetError()）：
GL_BGRA不存在所以我用GL_RGBA替换它，我的纹理很好地绑定到四边形（GL_RGBA8不起作用）
我仍然有一个绿色污点问题，但这必须是另一个问题：框架用YUV初始化？

用缩放纹理四边形替换gluScaleImage：但纹理未渲染

1 个答案: