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Learn how Singular Value Decomposition reduces image size, eliminates redundant data, and saves storage space, all while preserving image quality. Explore the process and results of digital image compression using SVD.
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Digital Image Compression via Singular Value Decomposition Robert WhiteRay Buhr Math 214 Prof. Buckmire May 3, 2006
The Problem • High resolution digital images are dense files and take up lots of bandwidth • Cost of: • time spent online • accepting large files • capable machinery
The Solution • Using Singular Value Decomposition, we can reduce the size of the image’s matrix • Eliminates the end SVDs • Cuts out the boring parts
The Matrix/Image • Matrix represents a grayscale image (126x128) • Each component is represented by a # 0-255
The Process • A = U*Σ*VT • ∑= the normalized singular values (√λ for ATA) • V= columns are eigenvectors of ATA • U= columns are eigenvectors of AAT • [U,S,V]=svd(A) factors A in Matlab
For Example A = 4 x 4 =
U = ∑ = VT =
Taking Care of Business • SVD, singular values = rank(A) • A = σ1u1vT1 + …σkukvTk + 0*uk+1vTk+1 • Approximate A by eliminating small singular values
The Pictures The original, k=126 k=4
The Pictures k=8 k=20
The Pictures k=50 Original, again, k=126
The Results How much space is this process saving? 4 + 4(126) + 4(128) = 1020 8 + 8(126) + 4(128) = 2040 20 + 20(126) + 20(128) = 5100 (~31.6%) 50 + 50(126) + 50(128) = 12750 (~79.0%) (126)*(128) = 16128! x + x(126) + x(128) = 16128, x ≈ 63.247