Save image data to sqlite - c++

Question

I have a function which loads an image from file and successfully creates an opengl texture from it.
/**
* #brief Loads a texture from file and generates an OpenGL texture from it.
*
* #param filename Path to the image file.
* #param out_texture Texture id the results are bound to.
* #param out_width Value pointer the resulting image width is written to.
* #param out_height Value pointer the resulting image height is written to.
* #param flip_image Stb indicator for flipping the image.
* #return true Image has been successfully loaded.
* #return false Failed loading the image.
*/
bool LoadTextureFromFile(const char *filename, GLuint *out_texture, int *out_width, int *out_height, bool flip_image = false)
{
// Load from file
int image_width = 0;
int image_height = 0;
stbi_set_flip_vertically_on_load(flip_image);
unsigned char *image_data = stbi_load(filename, &image_width, &image_height, NULL, 4);
if (image_data == NULL)
{
std::cout << "ERROR::Tools::GLHelper::LoadTextureFromFile - Failed to load image from file '" << filename << "'." << std::endl;
stbi_image_free(image_data);
return false;
}
// Create a OpenGL texture identifier
GLuint image_texture;
glGenTextures(1, &image_texture);
glBindTexture(GL_TEXTURE_2D, image_texture);
// Set texture wrapping parameters
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
// Set texture filtering parameters
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image_width, image_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, image_data);
glGenerateMipmap(GL_TEXTURE_2D);
*out_texture = image_texture;
*out_width = image_width;
*out_height = image_height;
stbi_image_free(image_data);
return true;
}
What I am trying to do is to load an image via stbi_load like above and save it as BLOB to sqlite. Afterwards I want to be able to load the very same blob and create an opengl texture from it in a separate function.
In the first step I created a function which only loads the image:
unsigned char *ImageDataFromFile(const char *filename)
{
int image_width = 0;
int image_height = 0;
unsigned char *image_data = stbi_load(filename, &image_width, &image_height, NULL, 4);
if (image_data == NULL)
{
std::cout << "ERROR::Tools::GLHelper::LoadTextureFromFile - Failed to load image from file '" << filename << "'." << std::endl;
stbi_image_free(image_data);
}
return image_data;
}
In the next step I want to store this data into my sqlite database:
void DBConnector::AddImage(std::string name, unsigned char *data)
{
sqlite3_stmt *stmt;
int err = sqlite3_prepare_v2(db, "INSERT INTO images (name, img_data) VALUES (?, ?)", -1, &stmt, NULL);
if (err != SQLITE_OK)
{
std::cout << "ERROR::DATA::DBConnector - Failed to prepare sqlite3 statement: \n"
<< sqlite3_errmsg(db) << std::endl;
}
sqlite3_bind_text(stmt, 1, name.c_str(), -1, SQLITE_TRANSIENT);
sqlite3_bind_blob(stmt, 2, data, -1, SQLITE_TRANSIENT);
sqlite3_step(stmt);
sqlite3_finalize(stmt);
return;
}
Finally I connect the pieces:
unsigned char *image_data = Tools::FileHelper::ImageDataFromFile(selected_filepath.c_str());
db->AddImage("Foo", image_data);
What happens is that seemingly arbitrary data ends up in the database, which is definetly not image data. Sometimes the entries are just empty.
I suspect that I am handling the return type of stbi_load incorrectly, forcing random memory data into the database. Extract from stbi documentation:
The return value from an image loader is an 'unsigned char *' which points to the pixel data..
As I understand it I am simply passing the array pointer to sqlite3_bind_blob which accepts const void * just like glTexImage2D does. So why is it working for the one but not for the other? Or could the error source be somewhere else?
Edit
I also tried something else. Normally I pass -1 for size when calling i.e. sqlite3_bind_text, because the call will then automatically search for a null terminator. So I thought that I might have to pass the correct size in bytes when calling sqlite3_bind_blob because there might be no terminator there. So for an image with the size of 225 x 225 with 3 channels, I passed 225 * 225 * 3 as size parameter. Unfortunately this did not work either.