Exif thumbnail data

I'm currently a bit stucked in exif. I extract the thumbnail from the JPEG using GDI+ with C#. I wanted to get it unscaled so I used 0 as parameters to ImageWidth and ImageHeight parameters in the GetThumbnailImage function of the Image class. I always get an image size of 160x120 but I assume there can be different sizes and that GetThumbnailImage does not scale. I see that there could be a开发者_如何学Pythondditional exif data in the thumbnail, but I search for a fast way to decide whether ti scale the thumbnail or the primary image.

Is there any info about the thumbnail size in the primary images exif data? The tags I found until now doesn't seen to fit.

Has anyone done something similar?

Thanks in advance, Sascha

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Exif data depends on many factors. One is the camera creator. So there is no real answer. There may be information, but there must be no information. Also, information might be vendor specific...