Bitmap issue

Hi ,

Iam working on dynamic jpeg creation.am getting pixel,height and width from a webservice to my .aspx page.with all the three parameters from webservice am writing a functionlity in .aspx page to create a jpeg on bitmap.

sometimes jpeg is created and sometimes jpeg is distorted...i mean only half of the iamge can be seen,rest comes as a black..sometimes 25% of image coming rest black..why is that?...

u people may help me out to sort out this issue...
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