土壤-获取图像尺寸

Question

我已决定使用SOIL加载要用于我的项目的OpenGL图像。 我有此方法，该方法将加载图像并返回GLTexture，这是一个包含GLuint textureid和两个int宽度和高度的结构：

GLTexture loadTexture(const char *filePath) {
GLTexture texture = {};
int width;
int height;
unsigned char *data;

//Load Image File Directly into an OpenGL Texture
texture.id = SOIL_load_OGL_texture
    (
    filePath,
    SOIL_LOAD_AUTO,
    SOIL_CREATE_NEW_ID,
    SOIL_FLAG_MIPMAPS | SOIL_FLAG_INVERT_Y | SOIL_FLAG_NTSC_SAFE_RGB | SOIL_FLAG_COMPRESS_TO_DXT
    );

//Error Checking (Load Process)
if (texture.id == 0) {
    fatalError("SOIL Loading Error!");
}

//Generate and Bind Texture
glGenTextures(1, &(texture.id));
glBindTexture(GL_TEXTURE_2D, texture.id);

//Get Width, Height and Data of Image
glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_WIDTH, &width);
glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_HEIGHT, &height);
glGetTexImage(GL_TEXTURE_2D, 0, GL_RGBA, GL_UNSIGNED_BYTE, &data);

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, &data);
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_MIPMAP_LINEAR);
glGenerateMipmap(GL_TEXTURE_2D);

//Unbind Texture
glBindTexture(GL_TEXTURE_2D, 0);

//Return Texture
texture.width = width;
texture.height = height;
return texture;

}

据我所知，glGetTexLevelParameteriv（）应该返回绑定到宽度和高度的纹理的宽度，但是每当我加载图像时，它都会返回0。

我应该填写宽度和高度作为方法的参数，还是可以通过OpenGL获得它们？

Answer 1

SOIL_load_OGL_texture生成的纹理ID在

glGenTextures(1, &(texture.id));

行（glGenTextures创建一个新纹理，并将id存储在＆（texture.id）中）。 之后，所有操作都将在新创建的纹理上进行。 由于此新纹理为空，因此宽度和高度均为0。

我不确定在这里要实现什么，但是如果您只想加载纹理，那么此代码可能会起作用：

texture.id = SOIL_load_OGL_texture    (...);

//Error Checking (Load Process)
if (texture.id == 0) {
    fatalError("SOIL Loading Error!");
}

//Just bind and do not create a new texture
glBindTexture(GL_TEXTURE_2D, texture.id);

glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_WIDTH, &width);
glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_HEIGHT, &height);

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_MIPMAP_LINEAR);
glGenerateMipmap(GL_TEXTURE_2D);

//Unbind Texture
glBindTexture(GL_TEXTURE_2D, 0);

//Return Texture
texture.width = width;
texture.height = height;
return texture;