Colour quadrant correction



A useful utility is required that could be used in conjunction with output from the current favoured Colour Recovery software from the work of Richard Russell.

Resultant colours can sometimes be decoded with respect to the wrong U/V colour quadrant. A quadrant correction utility would enable manual adjustment of areas of picture that have been decoded to an incorrect quadrant. Generally, patches of affected colour occur, and they align with the block pattern used within the CR software.

If a coloured area lies within an incorrect quadrant, this of course means that the correct quadrant is one of three others.
The correct quadrant can be obtained simply by changing the sign of the colour values in the affected area: i.e. changing the sign of U, the sign of V, or the sign of both U and V.

Whilst the remedy is straightforward, identification of areas incorrectly decoded is less so. However, a manually aided process would lead to a correction workflow which would not necessarily be too time consuming to perform.

The requirement for the workflow (within a GUI environment) would be:
i) Select a UYVY video file to be the subject of correction.
ii) Navigate through frames in the file, and display an individual frame from the file which (the eye determines) contains a problem area (or areas).
iii) Click on a problem area to correct. The first click would define the borders of the problem area in an X, Y (and possible Z) dimension. Each subsequent click which would cycle through the four possibilities for quadrant signage. On each click, the values in the defined area would change to reflect the new signs, and the image displayed to the user be adapted until the user is satisfied with a chosen option.
iv) Navigation away from the adjusted frame would mean the user adjustment is persisted, and the workflow goes back to step (ii).
v) Save the corrected UYVY file.

If you feel you would like to write software to tackle the above, then please go ahead and write up your work under the 'Current Work' section. Finished utilities can be posted within the 'Utilities' section.

James Insell. 15/02/2009