1. A method for estimating quality of images compressed with a transformation based compression method, which uses estimated errors generated by quantization to obtain an image quality indicator and which does not require use of a reference image, the transformation based compression method including: transforming image data available in a two-dimensional discreet spatial domain into a two-dimensional discreet frequency domain by a transformation function resulting in at least one transformation block comprising at least one transformation coefficient, each transformation block of a same size including transformation coefficients representing same two-dimensional frequencies; scaling of the resulting transformation coefficients; and quantizing the scaled transformation coefficients using quantization parameters to set a number and/or size of quantization steps, wherein said method for estimating the quality of images comprises: calculating a probability of at least one specific quantized transformation coefficient value for at least all coefficients representing one identical two-dimensional frequency; estimating identifying parameters of at least one probability density function of non-quantized coefficient values from the quantized coefficient value probabilities, with a type of probability density function being preset; and calculating an image quality indicator from errors introduced by quantization, which are derived from probability density function parameters and quantization parameters.