I'm trying to create an mbtiles server in Go. The file follows the mbtiles spec.
The tile_data field is a BLOB and i'm trying to query the database and get the corresponding images (stored as blob types).
So far the queries are OK but i'm getting corrupted tile_data results.
I'm not sure how to map a SQLite BLOB to a proper Go data structure.
So far i tried using var tileData []byte without success following this github gombtiles sample. The return value gets me an array of only 4 bytes which i suspect is kinda true since when i see the BLOB as Text type in a SQLite GUI it gets me 4 characters too (something like ÿØÿà)
To summarize:
The tile_data is a BLOB (storing an image) and i can't get a proper conversion to a Go var.
How can i convert a BLOB to Image in Go ?
UPDATE:
The ÿØÿà characters are 0xFF 0xD8 0xFF 0xE0 which are indeed the start of the JPEG file. I'm using the same MBTile file that i use in an iOS app through the Mapbox iOS SDK, so the file isn't corrupted and i can actually see the BLOB images using a SQLite GUI. The MBTiles spec says that the field is a BLOB type, and indeed, that's the field type that i'm using.
Again, the database is fine, is the same one used by an external iOS app. I can even query other data with success.
For context this is my isolated code.
func TilesHandler(w http.ResponseWriter, r *http.Request) {
db, _ := sql.Open("sqlite3", "./mapSource.mbtiles")
defer db.Close()
rows, _ := db.Query("SELECT tile_data FROM tiles WHERE zoom_level = 10 AND tile_column = 309 AND tile_row = 569")
defer rows.Close()
var tileData []byte
for rows.Next() {
rows.Scan(&tileData)
}
w.Write(tileData)
}
The zoom and coordinates are hardcoded for simplicity. tiledata is returning the mentioned 4 bytes.
UPDATE 2:
Here is the output of one specific record of the tiles table. Notice that the tile_data field is a BLOB and at the bottom the GUI shows that 4 characters. That are the exact one that i'm receiving in the []byte array at my Go code.
So my question is: I have this BLOB image file in my database which is a jpeg image. How i read it and show it as an image in my web page ? I want to read that BLOB and return an image in my http request.
Tiles row sample:
Tiles fields types
