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Date Posted: 19:32:21 03/01/01 Thu
Author: Michel
Subject: Re: Grayscale JPEG and Palette
In reply to: Bob Villiers 's message, "Re: Grayscale JPEG and Palette" on 12:22:44 03/01/01 Thu


Hi Bob,

If the image was loaded by Envision, the ImageFormat property of TDibGraphic will be ifGray256 or ifColor256.

There is one situation though, when scanning a gray scale image from a scanner, the format returned if ifColor256. The only way to then tell the difference is to examine the entries in the palette and of all RGB values are the same in every entry.

Best regards,

Michel
>Michel,
>
>Thanks for the reply. I am quite happy with a Jpeg
>automatically producing a colour table and have been
>using PaletteIndex on my current project like a good
>Boy Scout. I am just trying to correct my
>understanding. Incidentally, TJpegImage only produces
>a palette if the line
>
>DIBNeeded:= True;
>
>is added. It then produces a palette of index 0 to 235
>grays and 236 to 255 indeterminate, which is curious.
>TDibGraphic produces a colour table with 256 greys
>very satisfactorily.
>
>The nagging question is how does it differentiate
>between a "Gray" image and a very desaturated colour
>image. Anyway, I can live without an answer <g>.
>
>Best wishes,
>
>
>Bob

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