Updated Source for Image Samples

Joe Stegman's WebBlog : Updated Source for Image Samples

Joe Stegman's WebBlog : Updated Source for Image Samples — Fri, 31 Oct 2008 08:27:08 GMT

PingBack from http://blogs.msdn.com/jstegman/archive/2008/10/30/updated-source-for-image-samples.aspx

re: Updated Source for Image Samples

adam11235 — Wed, 05 Nov 2008 07:39:57 GMT

Hi Joe,

I cannot find the BMPDecoder source that the BMPDecoderSample references..

Added BMP Decoder

Joe Stegman's WebBlog — Mon, 10 Nov 2008 22:58:59 GMT

I updated the Image Source samples to include the BMP Decoder (missing from my previous post).

re: Updated Source for Image Samples

Michaeljz — Wed, 12 Nov 2008 18:32:03 GMT

Thanks for the example of how to do this. I also found an example on Ian Griffith's blog and have built some practice applications using the technique.

Based on code inspection (not profiling) you could improve the PngEncoder performance substantially by rewriting the ComputeAdler32 function. It currently performs two modulus operations per byte endoded image (so typically six modulus operations per pixel) which is computationally expensive. Wikipedia.org has an example of optimized adler32 code -- short explanation is to perform the modulus only every 5552 iterations, because s1 and s2 are guaranteed not to overlow a 32bit int until then.

It's unfortunate that there isn't an alternative encoding method to use for PNG. You need to make three passes through the data -- once to copy the pixels which you do in a Write, once to computer adler32, and once to compute CRC. Not only that, but a change to a small part of the image requires reprocessing all of it for the adler32 computation.

Michael

Saknar du stöd för GIF och BMP-bilder i Silverlight?

Robert Folkesson — Tue, 09 Dec 2008 01:45:59 GMT

Joe Stegman som arbetar i Silverlight-teamet har satt ihop några demokodsprojekt som visar hur du kan

Links da Semana (18-22)

Gonçalo Chaves — Wed, 20 May 2009 13:12:09 GMT

Apesar de andar muito ocupado nestes últimos dias, com projectos importantes e de carácter importante