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Date Posted: 20:00:35 02/11/02 Mon
Author: Michel
Subject: Re: Fax TIFF in Fine Mode
In reply to: glub 's message, "Re: Fax TIFF in Fine Mode" on 04:57:51 02/09/02 Sat


Hi Glup,

You have surfaced interesting points. Envision currently assumes x and y resolutions are the same for display purposes.

I think both approaches are valid, but are different in their nature.

Solution 1 forces you to explicitely perform a transformation if the X/Y resolution is not the same.

Solution 2 would compensate without you knowing, so if you do a SaveToStream/File the dimensions of you image would have changed.

Sometimes a user wants to work in pixels, but when sending output to a printer, the resolution is important (where Envision does not handle different x/y resolutions).

Solution 1 would not interfere with any existing code which I think is important. The TAspectRatioTransform is actually just a TResizeTransform with the proper dimensions.

I think what we need is a simple function that returns a new size of graphic given an original size, original XDpi, original YDpi, destination XDpi, YDpi. Then this size could be used with the TResizeTransform. Or this could be a method of the TResizeTransform.

The same could be applied when printing on a printer that has a different x/y resolution.

Does that sound good?

Best regards,

Michel




>I have now looked deeper in:
>
>It seams that TDibGraphic sets the X- and Y-Resolution
>of the DC correct, but if anyhow these values for the
>DC of the Form (actual the Monitor) are different, the
>aspect ratio of the displayed version of the graphic
>is not correct.
>Beside I would expect that the OS/GDI cares for this
>(would be a part of a "real" device _independent_
>bitmap) I see two possible solutions:
>
>1. I create for each DC I want to show the Dib on a
>"new" Dib with a aspect ratio changed to the ratio of
>the DC. This would ask for a TAspectRatioTransform.
>
>2. Everytime the TDibGraphic has to draw itself into a
>Cavas where the aspect ratio is different than the the
>own, it changes the aspect ratio "on-the-fly" with
>StretchBlt resp. StretchDIBits.
>
>The last version would be the more apealing I belive,
>but I see problems if code is asking for width and
>height. To solve this these both properties should
>!!!not!!! provide the sizes in pixel, but in mm, cm,
>inch, point or what-so-ever that is independent from
>the aspect ratio!
>
>Shouldn't option 2 with the change to the height and
>width property be implemented in TDibGraphic?
>
>Rgds
>
>Glup

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