the field of signal/image/video processing, computer vision, or data science in general (in both industry or academia). • Be able to understand and implement recent publications in that field. • Understand latest machine learning and computer vision techniques. Many deep learning concepts are based on tools that will be introduced in this class. NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 4/23
Computer Vision: Foundations and Applications (Stanford University) • Introduction to Computer Vision, CS5670, Spring 2023, Cornell Tech, www.cs.cornell.edu/courses/cs5670/2024sp/ • 16-385 Computer Vision, Spring 2020, Carnegie Mellon, www.cs.cmu.edu/∼16385/ • YouTube lectures • Image and video Processing: From Mars to Hollywood with a Strop at the Hospital, Guillermo Sapiro • Intro to Digital Image Processing, Rich Radke • Various codes • www.numerical-tours.com NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 4/23
• Scene: Set of objects that are in the field of vision • Light source: Sun, ambient lighting, spotlights, ... NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 6/23
Matrix/Tensor • Function I : E −→ F • Distribution • Random field • Surface/sub-manifold • ... NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 6/23
a digital image into another image or extracting features, primitives, or information. NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 7/23
min I • Luminance: Lum = Mean (I) • Contrast: C1 = N i=1 M j=1 (I(i, j) − Lum)2 N.M , C2 = max I − min I max I + min I NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 13/23
no compression, high quality, large size. Good for printing. • JPEG (.jpg, .jpeg): Joint Photographic Experts Group, Lossy compression, reduced size. Good for digital cameras, web use. • GIF: Graphics Interchange Format, used for web graphics, can be animated, limited to 256 colors, allow for transparency, small size. • PNG: Portable Network Graphics , lossless, support 16 million colors. • EPS (.eps) Encapsulated PostScript, vector file type, can be opened in applications such as Adobe Illustrator or CorelDRAW. • RAW Image Files (.raw, .cr2, .nef, .orf, .sr2, dicom, ...): created by a camera or scanner, hold a lot of information (intensities + metadata), need to be processed in an editor. NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 14/23
inch (1 inch = 2.54 cm), ppp : points par pouce • Number of ”physical” pixels in an inch of a printed document. • ppc: points per centimeter ; ppm : points per millimeter • ppi (pixels per inch): # of ”squared” pixels in an inch of a screen. NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 19/23
to use three parameters • Physical dimensions of the final image (on a screen, printed) or of the source image (page to be scanned) - e.g., 30 x 20 cm • Final resolution - e.g., 118 ppc • Image size (in pixels) - e.g., 3072 x 2048 pixels NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 19/23
want to print a 13 x 10 cm photo. Your printer asks you to provide images with a resolution of at least 300 dpi. • minimal width: 13x300/2,54=1535 pixels • minimal height: 10x300/2,54=1181 pixels. NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 19/23
screen set at 75 ppi displays a photo with dimensions of 15 x 12 cm. What is the size of the image in pixels? • 75ppi=75/2,54 pixels/cm • Largeur de l’image : 15*75/2,54 = 443 px • Hauteur de l’image : 12*75/2,54 = 354 px NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 19/23
low sampling frequency • The bands change direction and thickness NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 19/23
low sampling frequency • The bands change direction and thickness. NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 19/23
0 1 i j + ti tj • Rotation: x′ y′ = cos θ sin θ − sin θ cos θ x y + 0 0 • Coordinates relative to the center of the image • Exercise: Implement and run simulations. NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 21/23
pixel values at non-integer coordinates. • It is used in various applications such as resizing, rotating, and warping images. • Types of Image Interpolation • Replication • Nearest Neighbor Interpolation • Bilinear Interpolation • Bicubic Interpolation NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 22/23
the value of the nearest pixel is assigned to the interpolated pixel. • Formula: I(x′, y′) = I(round(x), round(y)) Where: • I(x′, y′) is the intensity value at the point (x′, y′) in the output image. • I(x, y) is the intensity value at the point (x, y) in the input image. • round(x) and round(y) round the coordinates to the nearest integer, representing the nearest pixel in the input image. NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 22/23
the closest 2 × 2 neighbors (four nearest pixels) to estimate the new pixel value. The interpolation is performed first in one direction (e.g., x-axis) and then in the other (y-axis), resulting in a smoother image than Nearest Neighbor. • Formula: I(x′, y′) = 1 i=0 1 j=0 I(x + i, y + j)(1 − |x′ − (x + i)|)(1 − |y′ − (y + j)|) The weights (1 − |x′ − (x + i)|) and (1 − |y′ − (y + j)|) are proportional to the distance of (x′, y′) from the corresponding neighboring pixels. NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 22/23
4 neighbors (16 pixels) to estimate the new pixel value using cubic polynomials. • Formula: I(x′, y′) = 2 i=−1 2 j=−1 I(x + i, y + j)W (i, x′)W (j, y′) where W (k, t) is the cubic weight function. NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 22/23
OpenCV library and that performs the following: 1. Read, display and save an image. 2. Manipulate pixels intensities and image channels. 3. Transform a matrix into a vector and vice-versa. 4. Compute and display some characteristics such as dynamic, luminance and contrast. 5. Perform compression by reducing the tonal resolution. 6. Perform different geometric transformations. 7. Perform a steganography. 8. Perform subsampling and upsampling. 9. Perfom image warping into a circle. NHSM - 4th year: Digital Image Processing - Introduction (Week 1) - M. Hachama ([email protected]) 23/23
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