土壤-獲取圖像尺寸

Question

我已決定使用SOIL加載要用於我的項目的OpenGL圖像。 我有此方法，該方法將加載圖像並返回GLTexture，這是一個包含GLuint textureid和兩個int寬度和高度的結構：

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;

}

據我所知，glGetTexLevelParameteriv（）應該返回綁定到寬度和高度的紋理的寬度，但是每當我加載圖像時，它都會返回0。

我應該填寫寬度和高度作為方法的參數，還是可以通過OpenGL獲得它們？

Answer 1

SOIL_load_OGL_texture生成的紋理ID在

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

行（glGenTextures創建一個新紋理，並將id存儲在＆（texture.id）中）。 之后，所有操作都將在新創建的紋理上進行。 由於此新紋理為空，因此寬度和高度均為0。

我不確定在這里要實現什么，但是如果您只想加載紋理，那么此代碼可能會起作用：

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;