CDIA Image Capture & Processing Techniques 4 — Questions and Answers
Question 1: What is the primary advantage of using lossless compression (e.g., CCITT Group 4) for black-and-white document images?
- Smaller file sizes than JPEG for photographic content
- Exact pixel-for-pixel reconstruction with no data loss (Correct answer)
- Faster scanning throughput
- Better color rendering for grayscale documents
Correct answer: Exact pixel-for-pixel reconstruction with no data loss
CCITT Group 4 (G4) is a lossless compression standard that reconstructs the exact original bitmap, which is critical for text and line-art documents where any distortion could impair readability or OCR.
Question 2: Which scanning artifact appears as a ghost image of the reverse side of a document showing through when scanning thin paper?
- Moiré pattern
- Bleed-through (Correct answer)
- Barrel distortion
- Newton's rings
Correct answer: Bleed-through
Bleed-through occurs when ink or print from the reverse side of thin paper is partially visible on the scanned image, which can be reduced using background suppression settings.
Question 3: In a document imaging system, what is the role of an image header file?
- Storing the pixel data of the scanned document
- Containing metadata about the image such as resolution, bit depth, color space, and compression type (Correct answer)
- Providing the OCR text layer for the document
- Encrypting the document content for secure transmission
Correct answer: Containing metadata about the image such as resolution, bit depth, color space, and compression type
Image header files (e.g., TIFF header) store metadata parameters that describe how the image data is structured, enabling software to correctly interpret and display the image.
Question 4: What does 'interpolated resolution' mean in scanner specifications?
- The true optical resolution as measured by the scanner's physical lens and sensor
- A resolution value achieved by software upsampling beyond the hardware's optical limit (Correct answer)
- The scanning speed measured in lines per second
- The number of colors the scanner can distinguish
Correct answer: A resolution value achieved by software upsampling beyond the hardware's optical limit
Interpolated resolution uses software algorithms to insert additional pixels between those actually captured, artificially increasing the reported DPI beyond the scanner's true optical capability.
Question 5: Which file format is specifically designed for multi-page document imaging and supports multiple compression types within a single file?
- JPEG
- PNG
- TIFF (Correct answer)
- BMP
Correct answer: TIFF
TIFF (Tagged Image File Format) supports multi-page documents and allows different compression algorithms (G4, LZW, JPEG, uncompressed) to be applied to individual pages within one file.
Question 6: What is 'zone OCR' and how does it differ from full-page OCR?
- Zone OCR processes only predefined regions of a document, while full-page OCR recognizes text across the entire page (Correct answer)
- Zone OCR uses higher resolution for better accuracy
- Zone OCR converts handwriting while full-page OCR handles printed text only
- Zone OCR applies to color documents while full-page handles black and white
Correct answer: Zone OCR processes only predefined regions of a document, while full-page OCR recognizes text across the entire page
Zone OCR restricts recognition to specified areas (zones) of a form or document, improving speed and accuracy by focusing on fields with known locations rather than processing the entire page.
Question 7: What is the purpose of scanner calibration using a white reference strip?
- Setting the mechanical paper feed tension
- Establishing a baseline white point so the scanner consistently represents pure white accurately (Correct answer)
- Determining the maximum scan resolution
- Aligning the scanner lamp with the optical head
Correct answer: Establishing a baseline white point so the scanner consistently represents pure white accurately
The white reference strip allows the scanner to normalize its output by defining the maximum reflectance value, ensuring consistent and accurate tonal representation across scans.
CDIA Image Capture & Processing Techniques 4
What is the primary advantage of using lossless compression (e.g., CCITT Group 4) for black-and-white document images?