C++ GDI+从文件加载图像，然后在卸载图像之前删除该文件

发布于 2024-10-17 06:08:51 字数 1043 浏览 3 评论 0原文

就像罐头上写的那样我正在使用 Bitmap::FromFile 从文件加载位图，但之后我想从磁盘中删除它。
问题是，Bitmap::FromFile 绝对锁定文件，防止任何更改/删除，直到卸载加载的图像

，这是因为我将位图存储在二进制文件中，所以我想按以下顺序执行操作：
1.从二进制文件中提取图像
2.加载图片
3.删除#1中提取的文件
（只是对我的图像资源进行一些基本保护，我只是不希望它们位于我的程序目录中）

即使像我的尝试一样从文件克隆加载的图像，Bitmap::FromFile 仍然会锁定文件以防止删除：

    Bitmap* tempbmp = Bitmap::FromFile(fileanddir.c_str(),false);
    Rect temprect( 0, 0, tempbmp->GetWidth(), tempbmp->GetHeight() );

    // make the image to be used as a clone to the temporary
    // bitmap to avoid file locking
    image_to_be_used = tempbmp->Clone(temprect, PixelFormatDontCare);

    // delete temporary loaded bitmap since it shouldn't be needed
    delete tempbmp;

    // delete the file itself, too bad the file is locked
    int theresult = remove(tocharptr(fileanddir)); 
    // returns -1, also: manually deleting at this point gives the error
    // that the file is being used by another person/program

知道如何我可以加载位图或以某种方式将其复制到内存中，这样文件本身就不会被锁定？
（所以我可以在加载后立即删除它）

原文

Simply what it says on the tin
I'm loading a bitmap from a file using Bitmap::FromFile but afterwards I want to delete it from the disk.
The problem is, Bitmap::FromFile absolutely locks the file from any changes/deletion until the loaded image is unloaded

This is because I'm storing the bitmaps in a binary file, so I want to do it in this order:
1. extract the image from binary file
2. load the image
3. delete the file extracted in #1
(just some basic protection for my image resources, I just don't want them sitting in my program directory)

Bitmap::FromFile still locks the file from deletion even when cloning the loaded image from the file like in my attempt:

    Bitmap* tempbmp = Bitmap::FromFile(fileanddir.c_str(),false);
    Rect temprect( 0, 0, tempbmp->GetWidth(), tempbmp->GetHeight() );

    // make the image to be used as a clone to the temporary
    // bitmap to avoid file locking
    image_to_be_used = tempbmp->Clone(temprect, PixelFormatDontCare);

    // delete temporary loaded bitmap since it shouldn't be needed
    delete tempbmp;

    // delete the file itself, too bad the file is locked
    int theresult = remove(tocharptr(fileanddir)); 
    // returns -1, also: manually deleting at this point gives the error
    // that the file is being used by another person/program

Any idea how I can load a bitmap or somehow copy it to memory so the file itself wouldn't be locked ?
(So i can delete it a moment after loading it)

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起风了 2024-10-24 06:08:51

你可以这样做

Gdiplus::Bitmap* LoadImageFromFileWithoutLocking(const WCHAR* fileName) {
    using namespace Gdiplus;
    Bitmap src( fileName );
    if ( src.GetLastStatus() != Ok ) {
        return 0;
    }
    Bitmap *dst = new Bitmap(src.GetWidth(), src.GetHeight(), PixelFormat32bppARGB);

    BitmapData srcData;
    BitmapData dstData;
    Rect rc(0, 0, src.GetWidth(), src.GetHeight());

    if (src.LockBits(& rc, ImageLockModeRead, PixelFormat32bppARGB, & srcData) == Ok)
    {
        if ( dst->LockBits(& rc, ImageLockModeWrite, PixelFormat32bppARGB, & dstData) == Ok ) {
            uint8_t * srcBits = (uint8_t *) srcData.Scan0;
            uint8_t * dstBits = (uint8_t *) dstData.Scan0;
            unsigned int stride;
            if (srcData.Stride > 0) { 
                stride = srcData.Stride;
            } else {
                stride = - srcData.Stride;
            }
            memcpy(dstBits, srcBits, src.GetHeight() * stride);

            dst->UnlockBits(&dstData);
        }
        src.UnlockBits(&srcData);
    }
    return dst;
}

You can do it this way

Gdiplus::Bitmap* LoadImageFromFileWithoutLocking(const WCHAR* fileName) {
    using namespace Gdiplus;
    Bitmap src( fileName );
    if ( src.GetLastStatus() != Ok ) {
        return 0;
    }
    Bitmap *dst = new Bitmap(src.GetWidth(), src.GetHeight(), PixelFormat32bppARGB);

    BitmapData srcData;
    BitmapData dstData;
    Rect rc(0, 0, src.GetWidth(), src.GetHeight());

    if (src.LockBits(& rc, ImageLockModeRead, PixelFormat32bppARGB, & srcData) == Ok)
    {
        if ( dst->LockBits(& rc, ImageLockModeWrite, PixelFormat32bppARGB, & dstData) == Ok ) {
            uint8_t * srcBits = (uint8_t *) srcData.Scan0;
            uint8_t * dstBits = (uint8_t *) dstData.Scan0;
            unsigned int stride;
            if (srcData.Stride > 0) { 
                stride = srcData.Stride;
            } else {
                stride = - srcData.Stride;
            }
            memcpy(dstBits, srcBits, src.GetHeight() * stride);

            dst->UnlockBits(&dstData);
        }
        src.UnlockBits(&srcData);
    }
    return dst;
}

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满地尘埃落定 2024-10-24 06:08:51

看一下Bitmap::FromStream。您应该能够使用 SHCreateStreamOnFileEx 打开文件上的 IStream。加载位图后，您可以安全地删除流，然后删除临时文件。

如果二进制文件仅使用支持的算法进行压缩，则将相应的标志传递给 SHCreateStreamOnFileEx 并让它读取存档，绕过将图像提取到临时文件中。否则可以实现IStream接口来读取二进制文件并直接提取图像数据。

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べ映画 2024-10-24 06:08:51

如果您对 MFC-OLE 示例感兴趣：

CFile file;
CFileException fe;
CString strFileName = "C:\\yours.bmp";

if (!file.Open(strFileName, CFile::modeRead | CFile::shareDenyNone , &fe))
{
    return;
}
COleStreamFile stream;
if(!stream.CreateMemoryStream(NULL))
{
    return;
}
BYTE buf[1024];
int readed = 0;
do
{
    readed = file.Read(buf,1024);
    stream.Write(buf,readed);
}
while(readed > 0);

file.Close();
stream.SeekToBegin();
USES_CONVERSION;
m_pImage = new Gdiplus::Bitmap(stream.GetStream( ));

if you interested in MFC-OLE sample:

CFile file;
CFileException fe;
CString strFileName = "C:\\yours.bmp";

if (!file.Open(strFileName, CFile::modeRead | CFile::shareDenyNone , &fe))
{
    return;
}
COleStreamFile stream;
if(!stream.CreateMemoryStream(NULL))
{
    return;
}
BYTE buf[1024];
int readed = 0;
do
{
    readed = file.Read(buf,1024);
    stream.Write(buf,readed);
}
while(readed > 0);

file.Close();
stream.SeekToBegin();
USES_CONVERSION;
m_pImage = new Gdiplus::Bitmap(stream.GetStream( ));

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~没有更多了~