Delphi – How to get the current view size for an image in Delphi 2009

delphisizetimage

I wish to get the current size for an image being displayed with TImage, this object has the Proportional property set to True and is aligned to Client with main form. So, when resizing the form I wanna get the current size for that image, not canvas size neither real size for that image. Getting the current size I can show what's the percentage for current image size respect to real image size.
Thanks in advance

Best Answer

You can compare Image1.Picture.Width or .Height with Image1.Width or .Height.

To know if the image is streched proportional using the horizontal or vertical dimension, you should compare the ratio's of the two:

if Image1.Width/Image1.Height > Image1.Picture.Width/Image1.Picture.Height then 
  Result:=Image1.Picture.Width/Image1.Width
else
  Result:=Image1.Picture.Height/Image1.Height;

using a mathematical trick to convert the divisions into multiplications, you can avoid the conversions into float values, which also calculate a bit faster by using:

if Image1.Width*Image1.Picture.Height >Image1.Picture.Width*Image1.Height then

Related Solutions

Delphi – How to get the Delphi IDE’s Main Form

The IDE's main form is Application.MainForm. My quick test design package:

procedure DoStuff(Form: TCustomForm);
var
  S: string;
begin
  S := Form.Caption;
  Form.Caption := S + ' - this one';
  try
    ShowMessage(Format('%s [%s] on monitor %d', [Form.Name, Form.ClassName, Form.Monitor.MonitorNum]));
  finally
    Form.Caption := S;
  end;
end;

initialization
  DoStuff(Application.MainForm);

This in my case displays "AppBuilder [TAppBuilder] on monitor 0" and I can see the " - this one" suffix in the main form's caption. What doesn't seem to work in your case?

Delphi – How to get the size of an image in bytes with Delphi

TImage does not have any way to determine the size of whatever graphic it happens to be holding at a given time. That's not its job. Its job is only to display things. The TGraphic object manages the in-memory representation, and it also determines how to draw itself onto a given canvas. TImage really knows nothing at all. TGraphic might, but it doesn't necessarily keep track of the file size; that might be different from the amount of memory necessary to have the data in memory.

The way to determine the size of a file is to have a file or something file-like, such as a stream. As you mentioned in your comment, you can save the image to a stream and then find out the size of the stream.

function GetGraphicSize(g: TGraphic): Integer;
var
  ms: TStream;
begin
  ms := TMemoryStream.Create;
  try
    g.SaveToStream(ms);
    Result := ms.Size;
  finally
    ms.Free;
  end;
end;

If that's too costly to compute each time you need the size, then remember the size from the first time you see the image so you don't need to computer it anew each time. How did the thumbnail list get its images to begin with? If they came from files, then you could have simply fetched the file size as you were generating the thumbnails.

Best Answer

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