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Date Posted: 14:44:25 05/02/00 Tue
Author: Jorge Neudorfer
Subject: Re: Size of selection in Cms with zoom
In reply to: Michel 's message, "Re: Size of selection in Cms with zoom" on 08:49:15 04/29/00 Sat

Can you helpme again.

I do this now
AnchoCms := 2.54 * (AnchoPixels / GetDeviceCaps(ImageScrollBox.Graphic.DC,LOGPIXELSX));

I do this Before
AnchoCms := 2.54 * (AnchoPixels / ImageScrollBox.Graphic.XDotsPerInch);

I need to know cms when I make Zoom lens + or Zoom lens -
on the image

This an example with false data

Zoom lens 100 %
PixelsX = 160
PixelsY = 180
Width = 3.2
Height = 3,6

Zoom lens 120 % More pixels, same size
Pixelxs = 180
PixelsY = 200
Width = 3.2
Height = 3,6

Zoom lens 80 % Less pixels, same size
PixelsX= 140
PixelsY = 160
Width = 3.2
Height = 3,6

Why dont work ?

>
> Hi Jorge,
>
> What you are doing is correct. I guess what you are
> missing is the "Resolution" to obtain physical
> dimension.
>
> The window api calls,
>
> GetDeviceCaps(DeviceContext, LOGPIXELSX);
> GetDeviceCaps(DeviceContext, LOGPIXELSY);
>
> Allow obtaining the resolution in pixels per inch for
> a device context.
>
> If you are using a TDibGraphic, you can use the DC
> property as the device context.
>
> Best regards,
>
> Michel
>
> > Hello to all, I need to know the size of a selection
> > that I make on an image having in account the
> > percentage of Zoom lens that exists on the image.
> When
> > the percentage is in 100 percent I do it of the
> > following way
> >
> > Inches = pixels/ Resolution
> > Cms = 2.54 * Inches
> >
> > Thanks for your help
> >
> > Please a need do this

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