Re: [Lcms-user] Basic Sample Question

[Michael Z. <psy...@gm...>]

Hi Marti,

just tried your suggestion and it works perfectly now - was something 
wrong with the formatter.

This is the modified code creating the formatter for reference:

    cmsColorSpaceSignature outputColorSpace = cmsGetColorSpace(hOutProfile);
     cout << "Colorspace of the output profile: " << hex << 
(int)outputColorSpace << dec << endl;
     int nNumOutputChannels = cmsChannelsOf(outputColorSpace);
     int nOutputFormatter = BYTES_SH(1) | CHANNELS_SH(nNumOutputChannels);
     nOutputFormatter |= 
COLORSPACE_SH(_cmsLCMScolorSpace(outputColorSpace));
     int nNumBytes = T_BYTES(nOutputFormatter);
     cout << "Output Profile has " << nNumOutputChannels << " channels 
each with " << nNumBytes << " Bytes." << endl;


Thanks a ton

Michael
>
> Hi Michael,
>
> I think you are assuming T_BYTES() returns the number of bytes per
> pixel when it really returns bytes per channel. Also, you are mixing
> cmsColorSpaceSignature with formatters.
>
> Just use this:
>
> nOutputFormatter = BYTES_SH(1) | CHANNELS_SH(nNumOutputChannels);
>
> This is enough. You can do an additional colorspace check by using
>
> nOutputFormatter |=
> COLORSPACE_SH(_cmsLCMScolorSpace((cmsColorSpaceSignature(hProfile)));
>
> Plese note the "_" at the begin of _cmsLCMScolorSpace, and that means
> you should not need this function in normal operation. If fact, the
> colorspace (color model to be more precise) of the image is not given
> by the profile but by the image itself. As an example, I can embed a
> RGB profile into a CMYK image. Using the algorithm above would not
> work. I would check both color models to validate the profile before
> proceeding to do the color transformation.
>
> Regards
> Marti
>
>
>
>
> Quoting Michael Zauner <psy...@gm...>:
>
>> Hi,
>>
>> I do love little CMS very much - nice, small and quick.
>> But I do have an issue with a bit of code and I cannot see what I am
>> doing wrong.
>> Maybe one of you guys could help me and tell if I do anything obvious
>> stupid?
>>
>> The basic idea is that I do have an image with an embedded profile and
>> an external profile file.
>> The external profile can differ and may have e.g. 6 channels.
>> I want to transform the image with the external profile and read the
>> pixel values of the output channels.
>>
>> Here is an example code (leaving out only the input image specific
>> stuff), which is really a modified version of the basic example seen in
>> the tutorial:
>>
>> //START
>>
>> cmsHPROFILE hInProfile, hOutProfile;
>> cmsHTRANSFORM hTransform;
>>
>> //Width and height and pixel type are from the input image
>> int nInputPixelType = TYPE_BGRA_16;
>> int nWidth = xxx;
>> int nHeight = xxx;
>>
>> //Loading the profiles
>> hInProfile = cmsOpenProfileFromMem(memoryPointer,size);
>> hOutProfile = cmsOpenProfileFromFile(szProfileFile, "r");
>>
>> //Extracting information of the output profile
>> cmsColorSpaceSignature outputColorSpace = cmsGetColorSpace(hOutProfile);
>> int nNumOutputChannels = cmsChannelsOf(outputColorSpace); //This is 6 in
>> my example
>> //This formatter is used in the transformation
>> int nOutputFormatter = _cmsLCMScolorSpace(outputColorSpace);
>> int nNumBytes = T_BYTES(nOutputFormatter); //This is 4 in my example
>>
>> //I change now the formatter to have 1 byte instead as I want to use
>> that instead of 4 byte precision
>> if(nNumBytes != 1)
>> {
>>      //Clear the first 3 bits
>>      nOutputFormatter &= ~7;
>>      //Set it to 1 Bytes
>>      nOutputFormatter |= 1;
>>      //Retrieve the value again (making sure it is one byte)
>>      nNumBytes = T_BYTES(nOutputFormatter);
>> }
>>
>> //Create the transformation
>> hTransform = cmsCreateTransform(hInProfile, nInputPixelType,
>> hOutProfile, nOutputFormatter,
>> INTENT_RELATIVE_COLORIMETRIC, 0);
>>
>> //Closing the profile
>> cmsCloseProfile(hInProfile);
>> cmsCloseProfile(hOutProfile);
>>
>> //Create a buffer to hold the transformed data
>> int nNewSizeInBytes = nNumOutputChannels * nHeight * nWidth * nNumBytes;
>> char* szData = new char[nNewSizeInBytes];
>> memset(szData,0,nNewSizeInBytes);
>>
>> //Transform the data
>> int nRowLengthInBytes = nNumOutputChannels*nNumBytes*nWidth;
>> for(int i = 0; i < nHeight; ++i)
>> {
>>      char* pixelBuffer = READ_BUFFER_FROM_IMAGE_FOR_ROW(i);
>>      cmsDoTransform(hTransform, pixelBuffer,szData + i
>> *nRowLengthInBytes, nWidth);
>> }
>>
>> //END
>>
>> The issue is that the transformation does work - I do get the data for
>> each channel. But the transformed image data is only 1/3 wide (the
>> height does match) - the other 2/3 of the image are untouched (e.g. when
>> I initialize szData with white instead of black, it remains white).
>> I must be doing something really stupid - but I cannot see what is 
>> wrong?
>>
>> Any help or pointers are highly appriciated.
>> It would help me to know if the litte CMS code is ok but I have an issue
>> either in the input buffer or the output buffer?
>>
>> Thank you very much in advance
>>
>> Michael
>>
>> ------------------------------------------------------------------------------ 
>>
>> Try New Relic Now & We'll Send You this Cool Shirt
>> New Relic is the only SaaS-based application performance monitoring 
>> service
>> that delivers powerful full stack analytics. Optimize and monitor your
>> browser, app, & servers with just a few lines of code. Try New Relic
>> and get this awesome Nerd Life shirt! 
>> http://p.sf.net/sfu/newrelic_d2d_may
>> _______________________________________________
>> Lcms-user mailing list
>> Lcm...@li...
>> https://lists.sourceforge.net/lists/listinfo/lcms-user
>>
>
>
>
>