Zero-decode image dimension parser. Reads width/height from raw file header bytes (~1µs, no GPU involvement). Supports JPEG (SOF0/SOF1/SOF2), PNG (IHDR), and WebP (VP8/VP8L/VP8X). Returns null for unknown formats — caller falls back to probe decode.
Zero-decode image dimension parser. Reads width/height from raw file header bytes (~1µs, no GPU involvement). Supports JPEG (SOF0/SOF1/SOF2), PNG (IHDR), and WebP (VP8/VP8L/VP8X). Returns null for unknown formats — caller falls back to probe decode.