c++ - OpenGL纹理奇怪的颜色

Question

我正在为颜色条绘制 OpenGL 纹理。输入图像来自OpenCV，因此其格式为BGRA。输出格式为RGBA。

我是这样画的:

// This drawer is for a texture
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, m_colorbarTextureID);

glBegin(GL_QUADS);

int width = m_colorbar.cols;
int height = m_colorbar.rows;

static const float inverse_scale = 2; // inverse scale value to resize the colormap image

float x = static_cast<float>(width) / (2 * inverse_scale);
float y = static_cast<float>(height) / (2 * inverse_scale);

static const float border = 10;

// Send the texture to minz in order to guarantee it will show up behind all the other elements
glTexCoord2f(0.0f, 0.0f); glVertex3f(m_lastCx - x - border, border, static_cast<GLfloat>(m_min2DDepth));
glTexCoord2f(0.0f, 1.0f); glVertex3f(m_lastCx - x - border, border + y, static_cast<GLfloat>(m_min2DDepth));
glTexCoord2f(1.0f, 1.0f); glVertex3f(m_lastCx - border, border + y, static_cast<GLfloat>(m_min2DDepth));
glTexCoord2f(1.0f, 0.0f); glVertex3f(m_lastCx - border, border, static_cast<GLfloat>(m_min2DDepth));

glEnd();

glDisable(GL_TEXTURE_2D);

这是我创建它的方式:

glEnable(GL_TEXTURE_2D);

// Resize image
cv::Mat colorbar_flip;
cv::resize(m_colorbar, colorbar_flip, cv::Size(), m_colorbarScale, m_colorbarScale);

// Flip y axis due to openGL convention (0 on bottom, positive pointing up)
cv::flip(colorbar_flip, colorbar_flip, 0);
glGenTextures(1, &m_colorbarTextureID);

if (m_colorbarTextureID == 0) {
    LoggerPublic::debug("Error creating colorbar texture");
    return;
}

glBindTexture(GL_TEXTURE_2D, m_colorbarTextureID);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

// Set texture clamping method
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);

//use fast 4-byte alignment (default anyway) if possible
//glPixelStorei(GL_UNPACK_ALIGNMENT, (colorbar_flip.step & 3) ? 1 : 4);
//set length of one complete row in data (doesn't need to equal image.cols)
//glPixelStorei(GL_UNPACK_ROW_LENGTH, static_cast<GLint>(colorbar_flip.step) / static_cast<GLint>(colorbar_flip.elemSize()));


glTexImage2D(GL_TEXTURE_2D,   // Type of texture
    0,                          // Pyramid level (for mip-mapping) - 0 is the top level
    GL_RGBA,                    // Internal colour format to convert to
    colorbar_flip.cols,         // Image width
    colorbar_flip.rows,         // Image height
    0,                          // Border width in pixels (can either be 1 or 0)
    GL_BGRA,                    // Input image format (i.e. GL_RGB, GL_RGBA, GL_BGR etc.)
    GL_UNSIGNED_BYTE,           // Image data type
    colorbar_flip.ptr());       // The actual image data itself

glDisable(GL_TEXTURE_2D);

wglMakeCurrent(nullptr, nullptr);

但是，我得到了这个奇怪的输出，在它应该是白色的地方带有蓝色调:

有什么问题吗？

编辑

也许这与仅使用 RGB 颜色绘制 3d 顶点有关，使用 glVertex3f 和 glEnableClientState(GL_COLOR_ARRAY)

Answer 1

这里的问题似乎是纹理的颜色是用顶点颜色调制的。默认情况下，glTexEnv 设置为 GL_MODULATE，这基本上意味着来自纹理的颜色与顶点颜色相乘。

您可以更改模式以仅使用纹理颜色

glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE)

旁注:固定功能管道非常陈旧且已弃用，因此如果没有充分的理由使用它，应该避免使用它。