Shape-adaptive tarp coding

An embedded wavelet coder is proposed for arbitrarily shaped image objects. Contrary to the popular approach of considering transparent regions surrounding image objects as permanently insignificant, the proposed coder imposes no assumptions on the significance state of unknown transparent regions. Instead, the proposed shape-adaptive tarp coder employs a simple algorithm called tarp filtering to produce a probability estimate of coefficient significance which propagates unchanged across transparent regions. Experimental results show that the shape-adaptive tarp coder offers coding performance superior to a popular zerotree-based technique and equivalent to a popular method based on context conditioning.