Issue with converting from 16bit signed to 8bit unsigned while decompressing and reconstructing one JPEG.

Issue with converting from 16bit signed to 8bit unsigned while decompressing and reconstructing one JPEG.

Hi, I am using intel IPP library for decompressing the JPEG. Internally I am using "ReconstructMCURowLS" method of the the class "jpegdec.cpp" for reconstructing the JPEG. Reconstruction is successful but while converting 16bit signed to 8bit unsigned, I am geting all the "pDst8u" 0xff instead of 0x00. And resulting all colours(near to black) becomes white. Below is the code path which is getting executed...... { ...... ...... ....... if(m_dst.precision <= 8) { dstStep = curr_comp->m_cc_step; pDst8u = curr_comp->GetCCBufferPtr(thread_id); } ....... .......... ............ ........ status = ippiReconstructPredRow_JPEG_16s_C1( ptr,pPrevRow,pCurrRow,m_dst.width,m_ss); ......... ............ .......... .......... ........ status = ippiConvert_16s8u_C1R(pPrevRow,m_dst.width*sizeof(Ipp16s),pDst8u,dstStep,roi); } Here I am not getting the expected result i.e. status should be "zero". I have doubt here, am I using the wrong method to convert from 16s to 8u? or pDst8u, whatever we are getting in one of the the previous steps is wrong? Can someone please help me in this topic? Thanks and Regards Krushna Prasad
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Hal's picture

Hi Krushna,

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Hal G.
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Thanks Hal. I have posted the same topic in the IPP forum.

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