# Egg inspection and grading glossary > This glossary defines, in one or two sentences, the terms used in shell-egg grading and in computer-vision inspection. It brings together the vocabulary of the regulations (candling, Class A, shell membranes) and of the technology (segmentation, watershed, mathematical morphology), so producers and engineers speak the same language. Updated: 2026-10-09 · URL: https://vigiovo.com/en/resources/glossary · Português: https://vigiovo.com/recursos/glossario.md ## Eggs and grading ### Candling Examining an egg against a bright light, which shows the air cell, yolk position, blood spots and fine cracks through the shell. It is a mandatory step in registered egg establishments in Brazil (RIISPOA, art. 223). ### Check (cracked egg) An egg with a broken or cracked shell whose shell membranes are intact and whose contents are not leaking (7 CFR 57.1). ### Hairline crack A crack so fine that it does not show under normal light. It is detected by candling or acoustic testing, not by an ordinary camera. ### Leaker An egg whose shell and shell membranes are broken so that the contents are exposed or leaking (7 CFR 57.1). ### Dirty egg An egg with an unbroken shell that has adhering dirt or foreign material, such as faeces, blood, soil or yolk (7 CFR 57.1). It does not meet Class A, which requires a clean shell. ### Cuticle A thin film that covers the shell and helps seal its pores. Washing can remove it, one reason the European Union bans washing Class A eggs. ### Shell membranes The two membranes just under the shell. When they are intact in a clean cracked egg, the egg can still go to industrial processing in Brazil (RIISPOA, art. 227). ### Air cell The air space at the broad end of the egg, visible when candling. For Class A it must not exceed 6 mm in height and must be stationary. ### Class A The top quality class for table eggs in Brazil and the EU: shell and cuticle of normal shape, clean and undamaged, plus interior requirements (RIISPOA art. 225; Delegated Regulation (EU) 2023/2465, art. 3). ### Class B Eggs that do not meet the Class A characteristics. In Brazil they go exclusively to industrial processing (RIISPOA, art. 226). ### Unverified egg In Vigiovo, an egg that cannot be seen whole (cut off by the frame edge, overlapping or abnormally shaped). It gets no grade and goes to manual review. ## Computer vision ### Colour segmentation Separating the pixels of interest by colour. Vigiovo uses HSV space to separate warm, bright shells from the grey, dark conveyor rollers. ### Distance transform An image in which each pixel holds its distance to the nearest edge of the shape. The centre of each egg becomes a peak, which makes touching eggs separable. ### Watershed A segmentation algorithm that treats the image as terrain and floods it from seeds. Where the basins meet defines the boundary between touching objects. ### H-maxima Regional peaks that rise at least h above their surroundings. Using them as seeds stops noise from splitting one egg in two. ### Mathematical morphology Shape operations, such as erosion, dilation, opening and closing, that clean masks, remove noise and highlight structures of a given size. ### Black-hat and top-hat Morphological filters that highlight fine details darker (black-hat) or lighter (top-hat) than their surroundings. They are the basis of image-based crack detection. ### Lab colour space A colour space that separates lightness (L) from colour (a and b). It reveals a stain of a different colour even when it is as bright as the shell. ### Shading surface A quadratic surface fitted by least squares to each egg's brightness. What falls well below it is a stain; the dome's natural gradient does not count. ### Deterministic computer vision Image processing with fixed rules, no trained models and no randomness. The same image with the same configuration always gives the same result. ### Reference radius (r) The typical egg radius in the image, measured on the first frame. Vigiovo's limits are multiples of r, so they hold for any camera resolution.