In this paper we present a generic content-based solution targeting at authenticating image in a semi-fragile way, which integrates watermarking-based approach with signature-based approach. Robust signatures are cryptographically generated based on invariant features called significance-linked connected component (SLCC) extracted from image content and are then signed and embedded back into the image again as watermarks, all in the wavelet domain. De-noising and morphological filtering are applied as pre-processing to tame some small perturbations on extracted features caused by various incidental distortions introduced in acceptable manipulations such as lossy compression, common image processing (blurring, sharpening, etc.) as well as watermarking. Error correcting coding is employed to further bridge between generated signatures and watermarks in a novel way: message bits are formed based on SLCC features, and parity check bits are taken as the seeds of watermarks. The generated s...