this reads .pfm files, i.e. simplistic netpbm little endian rgb floating
point maps. does not flip y coordinate.
filename the name of the input file, potentially containing %04d for sequencesstartid the index of the first file if loading a sequencenoise a the gaussian part of the noise estimationnoise b the poissonian part of the noise estimationoutput 32-bit floating point precision version of the f32 input file.