Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>If you're searching for an exact match (i.e. not a single pixel is different between the pattern you're looking for and the area in the image you want to find), you can actually use the Boyer Moore algorithm. It should be quite straight-forward to adapt it for looking for a 2D pattern.</p> <p>Let's say the pattern you look for is 20x20 pixels big. You build a table mapping greyvalues (or colors) to positions in the pattern image. Now can go through the search image in large strides, starting at pixel 19/19: If this pixel contains a greyvalue that's not contained in the pattern, you can skip this position and all the positions in a 20x20 area around it. So the next pixel you would check would be at 39/19 in the search image. If it contains a pixel that appeard e.g. in 3 positions in the pattern image, you can test these three positions relative to your current position in the search image (39/19).</p> <p>Note that this algorithm makes two assumptions:</p> <ul> <li>you can only find exact matches. This is practically impossible for real-world images, unless the pattern image was extracted directly from the search image. It's even unlikely to work if source and pattern images are e.g. scanned from the same photograph with the same scanner. It won't work if the pattern or source image were compressed using a lossy compression (like jpeg) after the pattern was extracted.</li> <li>The speedup depends on the number of greyvalues used. If you're looking for a binary pattern in a binary image, this algorithm won't run in O(n/m) time.</li> </ul>
    singulars
    1. This table or related slice is empty.
    1. POfast finding of small image in a bigger image
      singulars
      1. PTQuestion
    1. PTAnswer
    1. This table or related slice is empty.
    1. USNiki
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTDownMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COYes, the sub-image will be an exact match. I'll try to implement your algorithm. Thanks for your answer.
      singulars
      1. PO
      1. USBlizzy
    2. COAs noted ni other answers: The Boyer-Moore algorithm is not a good choice in this context.
      singulars
      1. PO
      1. USHannes Ovrén
    3. CO@kigurai: You seem to know more about the context than I do. Could you post some sample images maybe?
      singulars
      1. PO
      1. USNiki
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload