Simple Image Manipulation App (Flip, Rotate, Crop)

This is a simple image manipulation app with the following features:

• Load an image (Press L)
  
• Horizontal flipping (Press H)
  
• Vertical flipping (Press V)
  
• Rotation by pressing R (90 degree clockwise rotation) or SHIFT+R (90 degree counter-clockwise rotation)
  
• Cropping (click & drag mouse to define a crop rectangle)
  
• File navigation (press SPACE to load the next image in the active folder, press BACKSPACE to load the previous image in the folder).
  
• Save modified image (Press S)

Examples:

Attachment 182351

Attachment 182352

I wanted to learn more about Cairo graphics in RC6 by putting together a fully functional (albeit small) application. I haven't used RC6 Widgets for this project though, just vanilla VB6 forms & controls.

KNOWN BUGS:

Saving a cropped & rotated image will likely crop at the wrong location. Still trying to figure out why, and wouldn't mind some help with this part :) It might be nice if CCairoSurface had a Crop(X1, Y1, X2, Y2) method that would return a new CCairoSurface cropped out of the full-sized surface.

OTHER NOTES:

I'm not convinced I've gone about the Cairo stuff optimally - if Olaf or any other Cairo-knowledgable folks would be kind enough to review the code and make suggestions, it would be much appreciated.

Source Code (Requires RC6):

Attachment 182350

Hope you enjoy the demo, and maybe even learn something from it.

Quote:

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Originally Posted by jpbro

It might be nice if CCairoSurface had a Crop(X1, Y1, X2, Y2) method that would return a new CCairoSurface cropped out of the full-sized surface.

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I've so far not included this (because such a function would only save one line of code) -
but did so now for the sake of more convenience (it will be available in the next release).

Here's the "non-integrated" variant of that new method:

Code:

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Public Function CropSurface(SrcSrf As cCairoSurface, x, y, dx, dy) As cCairoSurface
  Set CropSurface = Cairo.CreateSurface(dx, dy)
      CropSurface.CreateContext.RenderSurfaceContent SrcSrf, -x, -y
End Function

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Olaf

Hi Olaf,

Thanks for the CropSurface function, and you're right that it's not a big savings in code, but it's a bit of convenience and nice to have.

I realize though, that I've made a mistake with my request. What I really think would be useful is a Crop method on a cCairoContext. For example, in my little demo app, the user might draw a crop rectangle, then rotate and flip the image. This is handled perfectly on screen - the crop rectangle, flips, scales, rotates, etc... synced to the transformations to the full size image. I want to then save the flipped and rotate image that is cropped at the right position. If I could pass the screen units to a crop method on the context, I don't have to figure out rotations/flips/etc... for positioning the crop rectangle myself since the context will transform the passed values automatically.

That said, maybe there's an easy way to do this that I a missing that wouldn't require such a method? I'll keep experimenting.

Thanks jpbro

Was wondering if you could possibly include a load picture function with a scrolled picture for "larger pictures"? I made a few fractal programs and was curious how it could be done with Cairo.