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Frans Vander Meiren · Guest

Hi

Anyone who can explain me to convert a 24-bit RGB bitmap (DIB-format) to a
32-bit CMYK bitmap by using an ICM colorprofile?
Thanks

Frans Vander Meiren

Damon Chandler (TeamB) · Guest

Hi Frans,
The TranslateBitmapBits() function should do this for you if you use a
CMYK profile as the "destination" profile. Here's a rough example that
creates a 32-bpp CMYK bitmap from a 24-bpp sRGB bitmap...

#include <icm.h>
#pragma link "mscms.lib"

Graphics::TBitmap* sRGB2CMYKBitmap(
Graphics::TBitmap& SrcBitmap,
AnsiString cmyk_profilename
)
{
// copy the file-name of the target (CMYK) profile
TCHAR tgt_profilename[MAX_PATH];
lstrcpyn(tgt_profilename,
cmyk_profilename.c_str(), MAX_PATH);

// initialize a PROFILE structure
PROFILE tgt_profile;
tgt_profile.dwType = PROFILE_FILENAME;
tgt_profile.pProfileData = static_cast<void*>(tgt_profilename);
tgt_profile.cbDataSize =
(lstrlen(tgt_profilename) + 1) * sizeof(TCHAR);

// create the color profile object
HPROFILE const hTgtProfile = OpenColorProfile(
&tgt_profile, PROFILE_READ, FILE_SHARE_READ, OPEN_EXISTING
);
if (hTgtProfile == NULL)
{
throw EWin32Error("OpenColorProfile() failed.");
}

// force the source bitmap to 24 bpp
SrcBitmap.PixelFormat = pf24bit;

// create the target bitmap object
std::auto_ptr<Graphics::TBitmap>
TgtBitmap(new Graphics::TBitmap());
TgtBitmap->PixelFormat = pf32bit;
TgtBitmap->Width = SrcBitmap.Width;
TgtBitmap->Height = SrcBitmap.Height;

//
// perform the color conversion...
//
try
{
// validate the profile's contents
BOOL is_valid = FALSE;
IsColorProfileValid(hTgtProfile, &is_valid);
if (!is_valid)
{
throw EWin32Error("bad profile");
}

// initialize a LOGCOLORSPACE struct
LOGCOLORSPACE lcs = {
LCS_SIGNATURE, 0x400, sizeof(LOGCOLORSPACE)
};
// sRGB color space
lcs.lcsCSType = LCS_sRGB;
// perceptual rendering intent
lcs.lcsIntent = LCS_GM_IMAGES;

// create a color transform object
HTRANSFORM const hColorTransform = CreateColorTransform(
&lcs, hTgtProfile, NULL, NORMAL_MODE + ENABLE_GAMUT_CHECKING
);
if (hColorTransform == NULL)
{
throw EWin32Error("CreateColorTransform() failed.");
}
try
{
// grab a pointer to the pixels
BITMAP src_bmp, tgt_bmp;
GetObject(SrcBitmap.Handle, sizeof(BITMAP), &src_bmp);
GetObject(TgtBitmap->Handle, sizeof(BITMAP), &tgt_bmp);

// color-match the bitmap's pixels
const bool match_ok =
TranslateBitmapBits(
hColorTransform,
src_bmp.bmBits, BM_RGBTRIPLETS,
src_bmp.bmWidth, src_bmp.bmHeight, 0,
tgt_bmp.bmBits, BM_CMYKQUADS, 0,
NULL, 0
);
if (!match_ok)
{
throw EWin32Error("TranslateBitmapBits() failed.");
}
}
__finally
{
// destroy the color transform object
DeleteColorTransform(hColorTransform);
}
}
__finally
{
// destroy the color profile object
CloseColorProfile(hTgtProfile);
}

// caller assumes ownership
return TgtBitmap.release();
}

The cmyk_profilename parameter must indicate the fully-qualified
file-name of a valid CMYK profile (you can get some here
[url]http://www.adobe.com/support/downloads/detail.jsp?ftpID=2348)[/url].

After the conversion, you can access the C, M, Y, and K values from the
returned CMYK bitmap by casting each scanline to a COLORREF and then
using the GetCValue(), GetMValue(), GetYValue(), and GetKValue()
macros. For example...

inline BYTE clip(int x)
{
if (x > 255) return 255;
if (x < 0) return 0;
return x;
}

void __fastcall TForm1::
ColorMatchButtonClick(TObject *Sender)
{
std::auto_ptr sRGB2CMYKBitmap(
*Image1->Picture->Bitmap, "c:\USWebUncoated.icc"
)
);

// convert back to uncalibrated RGB as a sanity check
int const cx = CMYKBitmap->Width;
int const cy = CMYKBitmap->Height;
for (int y0 = 0; y0 < cy; ++y0)
{
RGBQUAD* const pRGBRow = static_cast CMYKBitmap->ScanLine[y0]
);
COLORREF const* const pColorRow = static_cast<COLORREF*>(
CMYKBitmap->ScanLine[y0]
);
for (int x0 = 0; x0 < cx; ++x0)
{
int const c = GetCValue(pColorRow[x0]);
int const m = GetMValue(pColorRow[x0]);
int const y = GetYValue(pColorRow[x0]);
int const k = GetKValue(pColorRow[x0]);

pRGBRow[x0].rgbRed = clip(255 - (c + k));
pRGBRow[x0].rgbGreen = clip(255 - (m + k));
pRGBRow[x0].rgbBlue = clip(255 - (y + k));
}
}

// display the bitmap
Image2->Picture->Assign(CMYKBitmap.get());
}

HTH,
Damon (TeamB)

Frans Vander Meiren · Guest

Thanks Deamon

Greetings, Frans Vander Meiren

"Damon Chandler (TeamB)" <dmc27 (AT) cornell (DOT) edu> schreef in bericht
news:4007A334.69D35C77 (AT) cornell (DOT) edu...