frey

hey, sorry about the late notice but I’m performing at a placard (headphone) concert tonight at 2300 CET (11am Saturday morning, New Zealand time) in Poitiers, France as part of the Make Art festival.

you should be able to listen to to it here:
http://makeart.goto10.org/2008/?page=streaming&lang=en

So, if you happen to be doing what the subject line says – drawing anything into a CGContextRef that was created using CGBitmapContextCreate – and you’re seeing nothing but black, the trick is the following: you have to memset the the pixel data to all 0xFF’s before you draw.

For example, to draw a PDF document reference by ‘document’:

// allocate pixels
unsigned char* pixels = new unsigned char[thumb_height*thumb_width*4];

// create context
CGContextRef context = CGBitmapContextCreate(pixels, thumb_width, thumb_height, 8, 4*thumb_width, CGColorSpaceCreateWithName( kCGColorSpaceGenericRGB ), kCGImageAlphaNoneSkipLast );

// clear
memset( pixels, 255, thumb_width*thumb_height*4 );

// render page 1 into the pixels array
CGPDFPageRef page = CGPDFDocumentGetPage( document, 1 );
CGContextDrawPDFPage( context, page );

(For some reason I just wasn’t able to create any kind of RGBA context with CGBitmapContextCreate() – I always had to use the skip-alpha enum. Weird.)

From April until July 2007 I was resident with the Modulate collective in Birmingham, UK. They hosted me and looked after me and generally provided an excellent environment for me to develop my practise, to work out some things about what i was doing, and to begin to explore the European side of the world. This residency was in fact the thing that first brought me from New Zealand to the UK, and it has led directly to the connections I have made in Europe and elsewhere. So I was and still am greatly honoured to have been selected by them to undertake it.

In March earlier this year I went back to Birmingham to visit them again, and to work on a little video collobarative project involving using audio to control live video. While I was there we spent a couple of hours talking together about what the residency meant to all of us. They have just put up the video and audio from these conversations on their weblog over here.

Lovely.