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Date Posted: 21:29:01 12/11/03 Thu
Author: Michel
Subject: Re: You have probably already answered this but...Help!
In reply to: Dave Bracken 's message, "Re: You have probably already answered this but...Help!" on 09:52:46 12/08/03 Mon

Hi Dave,

This issue has been brought up a few times. Right now there is some protection in


which limits the maximum zoom to 1000%, but on large images zooming 1000% just consumes too much memory.

The best solution I can see for now is to add a new propert to TImageScrollBox called MaxZoomPercent. You can lower the value to say 500% and see if it works in your case.

I will email you the new EnImgScr.Pas unit to test.

Best regards,


>I saw that in the demo, and i use it in my Zoom In
>function. But im not sure if that applies to the other
>situation. I am using the zoom to selection function.
>If a user selects a very small area and selects zoom
>to slection, i want to make sure that it does not try
>to zoom in too much. So, i guess my question is really:
>How do i determine the size that the zoom will become
>on a zoomtoselection call so that i may limit it?
>Thanks in advance,
>>Hi Dave,
>>The ZoomChange is triggered after the zoom is changed
>>so it does not help you to prevent the change. You
>>should simply apply the same logic when assign a new
>>zoom value to the TImageScrollBox.ZoomPercent
>>property. For example, in the DemoForm.Pas example,
>>this is done in the TMainForm.ZoomEditChange method.
>>Best regards,
>>>I need to know how to limit zooming in on an image to
>>>a certain percent. I tried testing the zoompercent in
>>>onzoomchanged, but that did not work. You can see it
>>>in the following code:
>>>procedure TForm1.ImageScrollBox1ZoomChange(const
>>>Sender: TImageScrollBox;
>>> const Zoom: Single);
>>> if ZoomedMax then begin
>>> exit;
>>> end;
>>> if ImageScrollBox1.ZoomPercent > 200 then begin
>>> Screen.Cursor := crHourGlass; //this also does
>>> Application.ProcessMessages;
>>> ImageScrollBox1.ZoomPercent := 200;
>>> ZoomedMax := true;
>>> Screen.Cursor := crDefault;
>>> end;
>>> Hpos := ImageScrollBox1.HorzScrollBar.Position;
>>> Vpos := ImageScrollBox1.VertScrollBar.Position;
>>>I tried to look through your example, and could not
>>>find any indication there either.
>>>I need to limit this because it severely slows down
>>>system, and takes up quite alot of memory to zoom
>>>I would appreciate any help you can give.

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