**3.1.3 Results and discussion**

In order to show its relevance, the Textural function is used in the energy function of a Maximum A Posteriori segmentation algorithm (Martinez de Guerenu et al. 1996). Figure 7 shows separately the Wheatear and Non-wheatear regions resulting from this segmentation stage. Wheatear region pictures show false positive wheatear detecton (leaves or stems classified as wheatears). Non-wheatear region pictures show false negative detection (wheatears that have been forgotten).

Both kind of erroneous classification are circled on the pictures.

Fig. 7. Wheatear and Non-wheatear region results for MAP segmentation

Texture, Color and Frequential Proxy-Detection

zoom of cut off disk.

Image Processing for Crop Characterization in a Context of Precision Agriculture 57

(a) (b)

(c) (d)

(a) (b)

(a) (b)

Fig. 10. Threshold image (a) and cleaned image of wheat detection (b).

Fig. 9. Image after inverse FFT(a) and threshold image (b).

Fig. 8. Example of wheat image (a), (b) its associated FFT projection, (c) cut off disk, (d)

For the whole set of sample images, 1 to 3 segmentation errors have been found for each image. As the images show an average of 20 wheatears, the error rate can be estimated around 10%. Most of the errors encountered are identified as badly lightened wheatears. This kind of error could be easily overcome by using artificial light instead of natural light conditions, or using color images instead of grey level images, as it will be shown in the next section.
