Re: GDI and image displays
From: Tim Wilson ("Tim)
Date: 11/24/04
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Date: Wed, 24 Nov 2004 10:16:35 -0500
So it sounds like you start with a gradient background on your form and then
you want to paint an image on top of that, correct? How are you painting the
gradient effect onto the form?
-- Tim Wilson .Net Compact Framework MVP "Glyn Meek" <gjmeek@earthlink.net> wrote in message news:LzUod.2551$NU3.2356@newsread1.news.pas.earthlink.net... > Tim, I think I have the mechanism down OK, but the problem is that I am > using transparent images and when I write one on top of the other, the > underlying original one shows through the 'transparent' parts and I want the > original background to show...so, I am assuming the following technique > (which may be my basic mistake in understanding the way graphics are > written!) > > 1) I have to capture the original background (which is a gradual shading) > before drawing the first image > 2) when 'overwriting' with a subsequent image, I have to rewrite the > original image back and then write the new image over that...correct? > ...or, does invalidate juts 'get rid of' the original image and leave me > with the bare form? If it does, then I did NOT realize that the images were > effectively laid down in layers! > > Glyn > > "Tim Wilson" <TIM(UNDERSCORE)WILSON(AT)ROGERS(PERIOD)COM> wrote in message > news:evXK5n$yEHA.1256@TK2MSFTNGP10.phx.gbl... > > So you're drawing one image and then you want to change and draw another > > but > > not have the original displayed anymore? Where are you calling DrawImage > > from? If you're performing your image drawing in the OnPaint override, or > > a > > Paint event handler, then you just need to cause a refresh using, as one > > option, the Invalidate method. Then simply draw the new image and do not > > draw the old one. If you are not drawing your images through the > > OnPaint/Paint options, is there a specific reason why? > > > > -- > > Tim Wilson > > .Net Compact Framework MVP > > > > "Glyn Meek" <gjmeek@earthlink.net> wrote in message > > news:nxomd.27892$KJ6.6979@newsread1.news.pas.earthlink.net... > >> I have a routine which uses the GDI to display an image using > > '.DrawImage'. > >> > >> Sections of the image have been made transparent using > >> '.MakeTransparent'. > >> > >> Everything works well... > >> > >> ...BUT, I later need to replace the original image with a second image, > > also > >> with some transparent sections and cannot seem to find a way to do this. > > If > >> I merely use 'DrawImage to write the new image, sections of the old image > >> show through where the new image is transparent. > >> > >> I have tried putting both images in Rectangles, and manipulating the > >> rectangles, but this doesn't seem to work either. > >> > >> I tried to find a way to capture (and then restore) the original > > background > >> on the screen before the first image was drawn, but is BitBlt the only > >> way > >> to do this? > >> > >> Any GDI experts out there that can give me a hint as to how to get rid of > >> the original image altogether? or do I need to dive into the arcane world > > of > >> BitBlt, and if so, anyone got a good reference? > >> > >> Regards > >> > >> Glyn J Meek > >> > >> > >> > > > > > >
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