NSImage to blob and blob to NSImage (SQLite, NSData)

Question

First of all, I know that I should not use an SQLite database to store image, but I only store favicon of website which are really small.

My problem is that I try to insert those favicon into the database (seems to work), I convert the favicon to NSData with the -tiffrepresentation method of NSimage and then insert it to my database into a blob column:

 NSImage *favico = [webview mainFrameIcon];
[appDelegate insertBookmark:[titleField stringValue] url:[urlfield stringValue] data:[favico TIFFRepresentation]]

The SQLite method look like this:

-(void)insertBookmark:(NSString *)title url:(NSString *)url data:(NSData *)data
{
    NSData *imagedata = [[NSData alloc]initWithData:data]; 
    sqlite3 *database;
    if(sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) {
        NSString *query = [NSString stringWithFormat:@"INSERT INTO Bookmarks (title, url, image) VALUES ('%@', '%@', '%@')",title, url, data];
        const char *querychar = [query UTF8String]; 
        sqlite3_stmt *statement; 
        if (sqlite3_prepare_v2(database, querychar, -1, &statement, NULL) == SQLITE_OK)
        {
            int row =  3;
            sqlite3_bind_blob(statement, row, [imagedata bytes], [imagedata length], NULL);
            sqlite3_step(statement);
            sqlite3_finalize(statement);

        }
        else
        {
            NSLog(@"Error"); 
        }

        [databasePath retain]; 
        [databaseName retain]; 
    }
    sqlite3_close(database);
    [imagedata release]; 

}

When I look into the database I have value in the image column between <data> (normal ? )

Now when I extract the blob from the database and try to put it in my object I got null in the NSimage:

-(void) readDatabase {
// Setup the database object
sqlite3 *database;

bookmarks = [[NSMutableArray alloc] init];

// Open the database from the users filessytem
if(sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) {
    // Setup the SQL Statement and compile it for faster access
    const char *sqlStatement = "SELECT * FROM Bookmarks ORDER BY title ASC";
    sqlite3_stmt *compiledStatement;
    if(sqlite3_prepare_v2(database, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK) {
        // Loop through the results and add them to the feeds array
        while(sqlite3_step(compiledStatement) == SQLITE_ROW) {
            // Read the data from the result row
            NSString *aTitle = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 1)];
            NSString *aUrl = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 2)];
            NSData *data = [[NSData alloc] initWithBytes:sqlite3_column_blob(compiledStatement, 3) length:sqlite3_column_bytes(compiledStatement, 3)];
            NSImage *image = [[NSImage alloc]initWithData:data];
            bookmarkObject *bookmark = [[bookmarkObject alloc] initWithName:aTitle url:aUrl favico:image]; 

            [bookmarks addObject:bookmark];
            [bookmark release];
            [data release];
            [image release]; 



        }
    }
    // Release the compiled statement from memory
    sqlite3_finalize(compiledStatement);
    sqlite3_close(database); 
    [databasePath retain]; 
    [databaseName retain]; 


}

}

Thanks in advance

Thomas Zoechling Thomas Zoechling · Accepted Answer · 2011-05-01T10:03:31

The < and > around your actual data come from NSData. By using %@ in your format string and providing data, NSString sends description to data. [NSData description] wraps the content between < and >.

Another issue with your code is, that you seem to mix parameter-less & parameter prepared statements:

Either use stringWithFormat: to create a complete query statement
or use a query like INSERT INTO Bookmarks (title ...) VALUES (? ...) combined with sqlite3_bind_blob

The parameter syntax SQLite supports can be found here: http://www.sqlite.org/c3ref/bind_blob.html

NSImage to blob and blob to NSImage (SQLite, NSData)

1 Answers