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Re: completely and utterly confused with NSImage + MySQL

Subject: Re: completely and utterly confused with NSImage + MySQL
From: Hayden Stainsby <email@hidden>
Date: Sun, 26 Feb 2006 09:27:54 +0000
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I'm using the MySQL-Cocoa framework (http://mysql- cocoa.sourceforge.net/) which has a method that makes use of the mysql_hex_string function to turn binary data into hex. After that you need to get the binary data back again (since NSImage won't read straight from a hex string).

Here's the code to get your image back again.

--------
		int			i;
		const char	*thumbnailHex;

		thumbnailHex = [thumbnailDataHex bytes];
		for (i = 0; i < strlen(thumbnailHex); i += 2)  {
			char	aByte, tChar[2];
			
			tChar[0] = thumbnailHex[i];
			tChar[1] = thumbnailHex[i+1];
			
			tChar[0] -= 0x30;
			if (tChar[0] >= 0x0a)
				tChar[0] -= 0x07;
			
			tChar[1] -= 0x30;
			if (tChar[1] >= 0x0a)
				tChar[1] -= 0x07;
			
			aByte = tChar[0] << 4;
			aByte = aByte | (tChar[1]);
			
			[thumbnailData appendBytes:&aByte length:1];
		}
		thumbnailImage = [[NSImage alloc] initWithData:thumbnailData];
--------

thumbnailDataHex is taken straight out of the MySQL database.

It's tested and works just fine for me. Let me know if I've missed anything here.

--
Hayden


#!/usr/bin/perl
chop($_=<>);@s=split/ /;foreach$m(@s){if($m=='*'){$z=pop@t;$x
=pop@t;push@t,$a=eval"$x$m $z";}else{push@t,$m;}}print"$a\n";
        #http://occasionallyhuman.net/

On 25 Feb 2006, at 23:57, Eric Smith wrote:

That's pretty unsatisfying... let me ask another question. Is anyone on the list saving image data to a MySQL database? If so, how are you doing it? Writing a hex representation of the binary seems pretty safe.... but it doesn't work
Thanks,
Eric
On Feb 25, 2006, at 12:31 AM, Andrew Farmer wrote:
On 24 Feb 06, at 20:36, Eric Smith wrote:
If I take [tempData cString], run it through mysql_real_escape_string and then read it back into an image, using [[NSImage alloc] initWithData:...], the result is just a *portion* of the original image. How much? It depends on the level of compression. If I save an uncompressed image to the database, it comes back out as an entire image. What is going on here?!! Anyone have any ideas?
Two words for you: Null bytes.
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