[Gambas-user] an "Is this possible question" about images

[Rolf-Werner Eilert]

Am 15.04.2011 08:15, schrieb Kevin Fishburne:
> On 04/15/2011 12:47 AM, richard terry wrote:
>>
>>> Do you need it to look like a fisheye-style lens effect, or just
>>> box-zoom an area? If the latter this can be done easily in gb code.
>>
>> Just the box-zoom .
>>
>> Any change of you giving me a helping hand? I've not done anything much with
>> images or drawing.
>>
>> I'll mail you a sample png if you want - the purpose here is to magnify areas
>> of either skin, xray films or dermatascope images - all are images at the end
>> of the day.
>>
>> Its for our open - source medical records project that Ian and I are chuggling
>> slowly along with - not releasable as yet by I'm hoping that by the end of
>> 2011 it will be pretty much beta.
>>
>
> That is very cool. I'm doing a game so I know a little about images in gb.
>
> I'm going to assume that you're using Qt or GTK and not SDL or OpenGL,
> but correct me if I'm wrong. For those the easiest way to do graphics is
> with a DrawingArea control. After creating it on the form I'd change the
> Cached property to True so it will automatically redraw itself if
> something moves over it.
>
> You create image variables and load image files into them like this:
>
> Dim/Public someimage As Image
> someimage = Image.Load("FleshEatingVirusNooooo.jpg")
>
> You write images to the DrawingArea control like this:
>
> Draw.Begin(DrawingArea1)
>     Draw.Image(someimage, X, Y, [Width, Height, SrcX, SrcY, SrcWidth,
> SrcHeight])
>     ' Add more "Draw.Image" statements here to composite additional
> images into the DrawingArea.
> Draw.End ' Commits the composition to the DrawingArea so that it may be
> seen. May need a "Wait" statement if done repeatedly.
>
> The [bracketed] parameters are optional. someimage is the source and the
> DrawingArea is the target. You can specify a subset of the source (the
> area to be zoomed) by playing with SrcX and SrcY (upper-left corner of
> source to be drawn) and SrcWidth and SrcHeight (width and height
> relative to SrcX and SrcY of source to be drawn). You can scale the
> source by playing with Width and Height.
>
> So that the source image writes to the DrawingArea don't leave a trail,
> I'd first draw the main (unzoomed) image to the DrawingArea, then draw
> the zoomed area onto that for each "frame" that you draw. The logic
> would go something like:
>
> ' Create your image variables.
> ' Load images into your image variables.
> Draw.Begin(DrawingAreaControlName)
> ' Draw the main image into the DrawingArea.
> ' Draw part of the main image into the DrawingArea adjusted by cursor
> position, zoom area size and zoom level.
> ' Draw text or whatever else you need to into the DrawingArea.
> Draw.End
>
> To draw text, which is really cool, you may do something like this
> inside the Draw.Begin/End:
>
> Draw.Foreground = Color.Black
> Draw.Text("Look, it's text on an image with a crappy shadow!!!", X, Y)
> Draw.Foreground = Color.White
> Draw.Text("Look, it's text on an image with a crappy shadow!!!", X + 1,
> Y - 1)
>
> I don't have any project examples that are simple enough to demonstrate
> this, but if you're really having trouble I could put something together.
>

In order to have a magnifying box, you could simply load the whole 
picture into two DrawingAreas which are in two separate windows: The 
background window shows the whole picture but in a smaller scale, the 
little foreground window as a magnifier with a large DrawingArea holds 
the complete picture in a 1:1 scale. This DrawingArea would have to be 
moved within its window proportionally to the moves over and the scale 
of the background picture.

Hope I could make clear what I mean :-)

Rolf