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PO
 

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    <p>Okay, so having thought about this a bit longer, I've got a suggestion that seems like it's too simple to be efficient... I'd appreciate some feedback on whether it seems sensible!</p> <p>1) Since I can easily determine whether each <code>ridge_t</code> ridge segment at is connected to zero, one or two adjacent segments, I could colour each one appropriately (<code>LINE_NONE</code>, <code>LINE_END</code> or <code>LINE_MID</code>). This can easily be done in parallel, since there is no chance of a race condition.</p> <p>2) Once colouring is complete:</p> <pre><code>for each `LINE_END` ridge segment X found: traverse line until another `LINE_END` ridge segment Y found if X is earlier in memory than Y: change X to `LINE_START` else: change Y to `LINE_START` </code></pre> <p>This is also free of race conditions, since even if two threads are simultaneously traversing the same line, they will make the same change.</p> <p>3) Now every line in the image will have exactly one end flagged as <code>LINE_START</code>. The lines can be located and packed into a more convenient structure in a single thread, without having to do any look-ups to see if the line has already been visited.</p> <p>It's possible that I should consider whether statistics such as line length should be gathered in step 2), to help with the final re-packing...</p> <p>Are there any pitfalls that I've missed?</p> <p><strong>Edit:</strong> The obvious problem is that I end up walking the lines twice, once to locate <code>RIDGE_START</code>s and once to do the final re-packing, leading to a computational inefficiency. It's still appears to be O(N) in terms of storage and computation time, though, which is a good sign...</p>
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    1. POMemory-efficient line stitching in very large images
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    1. USPeter T.B. Brett
    1. USPeter T.B. Brett
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    1. COWhat happens if lines intersect?
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      1. USbdonlan
    2. COAh, balls. Good catch. Also, loop detection is required, I guess.
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      1. USPeter T.B. Brett
 

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