Bug: Copy image to clipboard doesn't work anymore ...

[Micha]

... if the image has an alpha channel. Only if I remove the alpha channel the image can be copied, for example to Photoshop.

In the past it was so - I double click an image in the browser and it open. I choosed per Ctl-H the visibility of the transparency and per Ctr-A and Ctrl-C I copied the image to the clipboard. It was the perfect workflow for me. Please bring it back soon as possible.

Best-
Micha

[xnview]

What's happened? I have no problem with other apps

[Micha]

Tested here too - in other apps it works. Looks like I need to install the old XnView and stay there.

[cday]

Looks like I need to install the old XnView and stay there.

Are you possibly using an old version of Windows?

Versions before 'XP are no longer formally supported, but whether that could possibly explain the issue I don't know...

[Micha]

No, I use Win 7 64 and I used XnView 1.97 for a long time without problems.

[XnTriq]

I have always struggled with 32-bit copy/paste, and I still use v1.97.8 as this is the last version that I can make it work in.

v1.97.8
32-bit Copy / Paste: works OK (as long destination image is also 32-bit)
32-bit Copy / Import clipboard: clipboard imported as 24-bit (without alpha layer), but then you can convert the newly created image to 32-bit, and paste the clipboard over it again, and now it works.

v1.98-v1.99
Neither of the above work for me (on XP SP3), I have tried every combination of alpha/32-bit settings I can find, and I just cannot get 32-pasting to work by any means.

I assume that the problem occurs in the pasting, not the copying, as I can copy from 1.98/99 then paste this into 1.97,
but I cannot copy (successfully) from 1.97 into 1.98/99.

[…]

UPDATE: Thank-you, the new v2.0.0 fixes these issues completely.

• Weird clipboard related bug
• Copy transparent image onto another image
• XnView does not paste alpha channel data into clipboard

[XnTriq]

1. Download logo.png.
2. Run clipbrd.exe.
3. Start XnView.
4. Select logo.png in the browser.
5. Go to Edit » Copy image data.
6. Switch to ClipBook Viewer.
7. Save the clipboard content as browser.clp.
   Result: transparency replaced by white background
8. Switch to XnView.
9. Open logo.png in the viewer.
10. Go to Edit » Copy.
11. Switch to ClipBook Viewer.
12. Save the clipboard content as viewer.clp.
    Result: all black

It might be like this article suggests, that the Clipboard object, working within Win32, is only able to manage bitmaps, which don't feature the transparent/partially transparent alpha channel. The OLE clipboard is more capable, it seems:

• Intro
• Vague support article
• A bit of discussion about the Win32 clipboard

However, the netez was the best article I found on the topic. (beware I haven't tested this myself)

I'm sure there is a right way of storing the alpha in CF_DIBV5, but it really doesn't matter. Applications already handle it inconsistently, so if you want your application to play nicely with others you can't use CF_DIBV5.

I researched copying and pasting transparent bitmaps a while ago. My aim was to successfully paste a transparent bitmap into two versions of Office and GIMP. I looked at several possible formats:

CF_BITMAP

Transparency is always ignored.

CF_DIB

Using 32bpp BI_RGB in the usual 0xAARRGGBB format. GIMP supports this but nothing else does.

CF_DIBV5

GIMP doesn't support this.

"PNG"

Paste supported: GIMP, Word 2000, Excel 2000, Excel 2007 and PowerPoint 2007.
Paste unsupported: Word 2007 and OneNote 2007.

All of these applications successfully export "PNG" if you copy a bitmap.

However, Word and OneNote 2007 will paste a PNG file copied from Explorer. So I came up with the following:

Solution for Copying

Convert your transparent bitmap to PNG format.

Advertise the following clipboard formats:

"PNG" - the raw PNG data.
CF_DIB - for applications (like paint) that don't handle transparency.
CFSTR_FILEDESCRIPTOR - make the PNG look like a file. The file descriptor should have an invented filename with a ".png" extension.
CFSTR_FILECONTENTS - the contents must be exposed as an IStream; just using an HGLOBAL doesn't seem to work. The data is identical to the "PNG" data.

Having done this I could successfully paste transparent bitmaps into GIMP, Office 2000 and Office 2007. You can also paste the PNG directly into an Explorer folder.

Update

I realised that I've only answered half the question. This is great for copying, but no use if you want to paste from an application that only copies CF_DIBV5 (like Firefox).

I'd recommend that you use "PNG" if it's available, otherwise fall back to CF_DIBV5, treating it as premultiplied. This will correctly handle Word 2010 (which exports "PNG"), Firefox and Chrome. XnView only exports non-multiplied CF_DIBV5, so this won't work correctly. I'm not sure you can do any better.

lscf - A Tool for Exploring Clipboard Formats

This is the source of a tool for displaying a list of available clipboard formats. It can also write one to a file. I called it lscf. Create a win32 console application in Visual Studio and paste this source over the main function. It has one very minor bug: it never displays the "Unknown format" error if you mistype a format name.

Code: Select all

#include <Windows.h>

#include <stdio.h>
#include <tchar.h>

#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))

LPCTSTR cfNames[] = {
    _T("CF_TEXT"),
    _T("CF_BITMAP"),
    _T("CF_METAFILEPICT"),
    _T("CF_SYLK"),
    _T("CF_DIF"),
    _T("CF_TIFF"),
    _T("CF_OEMTEXT"),
    _T("CF_DIB"),
    _T("CF_PALETTE"),
    _T("CF_PENDATA"),
    _T("CF_RIFF"),
    _T("CF_WAVE"),
    _T("CF_UNICODETEXT"),
    _T("CF_ENHMETAFILE"),
    _T("CF_HDROP"),
    _T("CF_LOCALE"),
    _T("CF_DIBV5")
};

int LookupFormat(LPCTSTR name)
{
    for (int i = 0; i != ARRAY_SIZE(cfNames); ++i)
    {
        if (_tcscmp(cfNames[i], name) == 0)
            return i + 1;
    }

    return RegisterClipboardFormat(name);
}

void PrintFormatName(int format)
{
    if (!format)
        return;

    if ((format > 0) && (format <= ARRAY_SIZE(cfNames)))
    {
        _tprintf(_T("%s\n"), cfNames[format - 1]);
    }
    else
    {
        TCHAR buffer[100];

        if (GetClipboardFormatName(format, buffer, ARRAY_SIZE(buffer)))
            _tprintf(_T("%s\n"), buffer);
        else
            _tprintf(_T("#%i\n"), format);
    }
}

void WriteFormats()
{
    int count = 0;
    int format = 0;
    do
    {
        format = EnumClipboardFormats(format);
        if (format)
        {
            ++count;
            PrintFormatName(format);
        }
    }
    while (format != 0);

    if (!count)
        _tprintf(_T("Clipboard is empty!\n"));
}

void SaveFormat(int format, LPCTSTR filename)
{
    HGLOBAL hData = (HGLOBAL)GetClipboardData(format);

    LPVOID data = GlobalLock(hData);

    HANDLE hFile = CreateFile(filename, GENERIC_WRITE, 0, 0, CREATE_ALWAYS, 0, 0);
    if (hFile != INVALID_HANDLE_VALUE)
    {
        DWORD bytesWritten;
        WriteFile(hFile, data, GlobalSize(hData), &bytesWritten, 0);
        CloseHandle(hFile);
    }

    GlobalUnlock(hData);
}

int _tmain(int argc, _TCHAR* argv[])
{
    if (!OpenClipboard(0))
    {
        _tprintf(_T("Cannot open clipboard\n"));
        return 1;
    }

    if (argc == 1)
    {
        WriteFormats();
    }
    else if (argc == 3)
    {
        int format = LookupFormat(argv[1]);
        if (format == 0)
        {
            _tprintf(_T("Unknown format\n"));
            return 1;
        }

        SaveFormat(format, argv[2]);
    }
    else
    {
        _tprintf(_T("lscf\n"));
        _tprintf(_T("List available clipboard formats\n\n"));
        _tprintf(_T("lscf CF_NAME filename\n"));
        _tprintf(_T("Write format CF_NAME to file filename\n\n"));
    }

    CloseClipboard();

    return 0;
}

[xnview]

Tested here too - in other apps it works. Looks like I need to install the old XnView and stay there.

which PS version do you have?

[Micha]

Adobe Photoshop Version: 11.0.2 CS4

[xnview]

Adobe Photoshop Version: 11.0.2 CS4

i've sent you a PM

[Micha]

test version works fine.

[xnview]

test version works fine.

ok, so it seems that photoshop doesn't like premultiplied component i'll add an option to use the old method...

[Micha]

Thank you.

[xnview]

Thank you.

i've sent you another PM

[XnTriq]

Freeware for analyzing clipboard content:

• Peter Johnson: Clipboard Format Spy
• Nir Sofer: InsideClipboard
• Jim Barry: Clipboard Spy (Softpedia)
• Karen Kenworthy †: Clipboard Viewer
• Comfort Software: Free Clipboard Viewer