3.3 Crop the Image

The region of the image that contains the lanes to be analyzed is delineated by a bounding box. This procedure is necessary to avoid the extraneous analysis of hand-written annotations on the edges of some autoradiograms and to speed the lane detection procedure.

• Pointer to Operations Submenu, click [Crop Image].

• Move the pointer to the upper left-hand corner of the sub-image to be analyzed, in most cases, the left margin of the leftmost lane, somewhat above the first band. The y position is not too critical, but the x position is crucial. The current (x, y) pointer position can be monitored in a small window just outside the upper left corner of the image. For the sample image k102.avg, a good (x, y) might be (30, 50).

• Depress and hold MB1, move the pointer to the lower-right corner of the sub-image and release MB1.

• The release of MB1 should be along the right margin of the rightmost lane and somewhat below the last band in the rightmost lane.

• While you have MB1 depressed, a small window appears in the upper left corner of the image; this window shows, from left to right, three pairs of numbers:
  - the 1st pair is the (x,y) coordinate pair when MB1 was depressed,

  - the 2nd pair is the current (x,y) coordinate pair,

  - the 3rd pair is the (width,height) pair.

  For image k102.avg, just before MB1 is released, these numbers might be:
  - initial (x, y) = (30, 50),

  - current (x, y) = (465, 390),

  - (width, height) = (435, 340).

• The rectangle that appears bounds the region to be analyzed.

• If you didn't get it quite right, you may repeat the procedure, beginning with the click of [Crop Image] . For example, if the top or bottom line of the bounding box appears to cut off one or more bands, the box may have to be extended.

Figure 3.5 shows the k102 image with a crop box. The hand annotations outside the crop box are excluded from analysis.

Figure 3.5: Image k102 with a crop box surrounding the region of interest