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Am trying to break image in shattered pieces, but am unable to catch the logic, please give me way how to achieve. enter image description here

I hope the below image can give my idea, what I want, Breaking the bitmap into a shattered pieces like triangle or any shape. later i will shuffle those bitmap shapes and giving puzzle to enduser rearrange them in order.

user3285681
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  • You tried BitmapShader? Also what's the goal for getting the image into shapes? Some puzzle game? Do you need them to be drag&dropped? – Niko Mar 10 '14 at 07:31
  • I think this could be useful http://stackoverflow.com/questions/21778690/triangle-shaped-imageview-with-drag-scroll-zoom-ontouch-android – Niko Mar 10 '14 at 07:38
  • Yes it is a puzzle game and drag and drop is also available, i never tried Bitmapshader – user3285681 Mar 10 '14 at 09:09

2 Answers2

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OK, if you want to rearrange the pieces (like in a jigsaw) then each triangle/polygon will have to appear in a rectangular bitmap with a transparent background, because that's how drawing bitmaps works in Java/Android (and most other environments).

There is a way to do this sort of masking in Android, its called porter-duff compositing. The Android documentation is poor to non-existent, but there are many articles on its use in Java.

Basically you create a rectangular transparent bitmap just large enough to hold your cut-out. Then you draw onto this bitmap a filled triangle (with transparency non-zero) representing the cut-out. It can be any colour you like. Then draw the cutout on top of the source image at the correct location using the Porter-Duff mode which copies the transparency data but not the RGB data. You will be left with your cutout against a transparent background.

This is much easier if you make the cutout bitmap the same size as the source image. I would recommend getting this working first. The downsides of this are twofold. Firstly you will be moving around large bitmaps to move around small cutouts, so the UI will be slower. Secondly you will use a lot of memory for bitmaps, and on some versions of Android you may well run out of memory.

But once you have it working for bitmaps the same size as the source image, it should be pretty straightforward to change it to work for smaller bitmaps. Most of your "mucking about" will be in finding and using the correct Porter-Duff mode. As there are only 16 of them, its no great effort to try them all and see what they do. And they may suggest other puzzle ideas.

I note your cutout sections are all polygons. With only a tiny amount of extra complexity, you could make them any shape you like, including looking like regular jigsaw pieces. To do this, use the Path class to define the shapes used for cutouts. The Path class works fine with Porter-Duff compositing, allowing cutouts of almost any shape you can imagine. I use this extensively in one of my apps.

Peter Webb
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I am not sure what puzzle game you are trying to make, but if there is no special requirements of the shattered pieces, only the total number of them which can span the whole rectangle, you may try doing the following steps, the idea is basically by knowing that n non-intersecting lines with two end points lie on any of the 4 edges of the rectangle, n+1 disjoint areas is formed.

  1. Create an array and store the line information

  2. For n times, you randomly pick two end points which lie on those 4 edges of the rectangle

    2a. Try to join these two points: start from either end point, if you get an intersection with another line you drew before, stop at the intersection, otherwise stop at the other end point

  3. You will get n+1 disjoint areas with n lines drawn

You may constrain your lines choosing if you have some special requirements of the areas.

For implementation details, you may want to have a look of dot product and euler's theorem

shole
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