Bob
Fri Feb 18 05:24:08 CST 2005
If you know the encoder CLSID there is no reason not to hard-code it. I
guess GDI+ was intended to evolve but has been kind-of shelved in favour of
Avalon. Bit of a shame really but that's life...
I reccommend not using the GetThumbnailImage method. It usually gives crude
results. It's better to do the job by drawing the whole image to a newly
created image of a different size. This works for reductions as well as
enlargements. The GDI+ FAQ has an example.
Bitmap is simply a storage medium. It does no manipulations of Graphics
beyond the getpixel / setpixel / rotateflip level. It's the Graphics object
that does interpolation etc so that's why you need one.
I have found that the bilinear interpolation is often nicer quality than the
bicubic. Perhaps this is just my sense of esthetics at work.
--
Bob Powell [MVP]
Visual C#, System.Drawing
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"TC" <aatcbbtccctc@yahoo.com> wrote in message
news:1108694957.937208.164530@g14g2000cwa.googlegroups.com...
> Hi folks
>
> Sorry if this is OT, but I got no joy in
> microsoft.public.win32.programmer/gdi.
>
>
> (1) I'm encoding to standard (built-in) formats: JPEG, BMP, GIF etc. I
> currently have the encoder CLSIDs hardcoded. Is that safe, or should I
> iterate the encoders at runtime, looking for ones with the relevant
> MIME types?
>
>
> (2) I'm using GdipGetImageThumbnail() to resample images smaller *or
> larger*. I've tried altering the interpolation mode to see if that
> makes any difference. It doesn't seem to. Here's what I'm doing:
>
> GdipGetImageGraphicsContext lOldBitmap, graphics
> GdipSetInterpolationMode graphics, <mode>
> GdipGetImageThumbnail lOldBitmap, W, H, lNewBitmap
>
>
> - Is GdipGetImageThumbnail() appropriate for resampling images larger,
> or is there a better way?
>
>
> - Should it use the interpolation mode that I have tried to set above?
>
>
> - Why does changing the interpolation mode, require a graphics context?
> Resampling is just a mathematical operation on the bitmap content. What
> does the graphics context contribute?
>
>
> TIA,
> TC
>