Convert BMP to jpg image through GDI +

 

Start with a C/C ++ source code and convert the image format in the main () function ~

// C/C ++ code
# Include <windows. h>
# Include <gdiplus. h>
# Include <stdio. h>
Using namespace gdiplus;

Int getencoderclsid (const wchar * format, CLSID * pclsid); // helper Function

Int main ()
{
// Initialize GDI +.
Gdiplusstartupinput;
Ulong_ptr gdiplustoken;
Gdiplusstartup (& gdiplustoken, & gdiplusstartupinput, null );

CLSID encoderclsid;
Encoderparameters;
Ulong quality;
Status Stat;

// Get an image from the disk.
Image * image = new image (L "shapes.bmp ");

// Get the CLSID of the JPEG encoder.
Getencoderclsid (L "image/JPEG", & encoderclsid );

// Before we call image: Save, We must Initialize
// Encoderparameters object. The encoderparameters object
// Has an array of encoderparameter objects. In this
// Case, there is onLy onE encoderparameter object in the array.
// The onE encoderparameter object has an array of values.
// In this case, there is onLy onE value (of Type ulong)
// In the array. We will let this value vary from 0 to 100.

Encoderparameters. Count = 1;
Encoderparameters. Parameter [0]. guid = encoderquality;
Encoderparameters. Parameter [0]. type = encoderparametervaluetypelong;
Encoderparameters. Parameter [0]. numberofvalues = 1;

// Save the image as a JPEG with quality level 0.
Quality = 0;
Encoderparameters. Parameter [0]. value = & quality;
Stat = image-> Save (L "shapes001.jpg", & encoderclsid, & encoderparameters );

If (STAT = OK)
Wprintf (L "% s saved successfully. \ n", l "shapes001.jpg ");
Else
Wprintf (L "% d attempt to save % s failed. \ n", stat, l "shapes001.jpg ");

// Save the image as a JPEG with quality level 50.
Quality = 50;
Encoderparameters. Parameter [0]. value = & quality;
Stat = image-> Save (L "shapes050.jpg", & encoderclsid, & encoderparameters );

If (STAT = OK)
Wprintf (L "% s saved successfully. \ n", l "shapes050.jpg ");
Else
Wprintf (L "% d attempt to save % s failed. \ n", stat, l "shapes050.jpg ");

// Save the image as a JPEG with quality level 100.
Quality = 100;
Encoderparameters. Parameter [0]. value = & quality;
Stat = image-> Save (L "shapes100.jpg", & encoderclsid, & encoderparameters );

If (STAT = OK)
Wprintf (L "% s saved successfully. \ n", l "shapes100.jpg ");
Else
Wprintf (L "% d attempt to save % s failed. \ n", stat, l "shapes100.jpg ");

Delete image;
Gdiplusshutdown (gdiplustoken );
Return 0;
}

Int getencoderclsid (const wchar * format, CLSID * pclsid). The function is a function in helper in Microsoft platform SDK. If not, add the following code implementation:

Int getencoderclsid (const wchar * format, CLSID * pclsid)

{
Uint num = 0; // Number of image encoders
Uint size = 0; // size of the image encoder array in bytes
Imagecodecinfo * pimagecodecinfo = NULL;
Getimageencoderssize (& num, & size );
If (size = 0)
Return-1; // failure

Pimagecodecinfo = (imagecodecinfo *) (malloc (size ));
If (pimagecodecinfo = NULL)
Return-1; // failure

Getimageencoders (Num, size, pimagecodecinfo );
For (uint J = 0; j <num; ++ J)
{
If (wcscmp (pimagecodecinfo [J]. mimetype, format) = 0)
{
* Pclsid = pimagecodecinfo [J]. CLSID;
Free (pimagecodecinfo );
Return J; // success
}
}
Free (pimagecodecinfo );
Return-1; // failure
}

Of course, we can also encapsulate them in the form of functions. The following are some simple function examples. You can modify them as needed:

// Save a bitmap * as a jpg image

Void SaveFile (Bitmap * pimage, const wchar_t * pfilename)
{
Encoderparameters;
CLSID jpgclsid; getencoderclsid (L "image/JPEG", & jpgclsid );
Encoderparameters. Count = 1;
Encoderparameters. Parameter [0]. guid = encoderquality;
Encoderparameters. Parameter [0]. type = encoderparametervaluetypelong;
Encoderparameters. Parameter [0]. numberofvalues = 1;

// Save the image as a JPEG with quality level 100.
Ulong quality;
Quality = 100;
Encoderparameters. Parameter [0]. value = & quality;
Status status = pimage-> Save (pfilename, & jpgclsid, & encoderparameters );
If (status! = OK)
{
Wprintf (L "% d attempt to save % s failed. \ n", status, pfilename );
}
}

 

// Save the current screen as a jpg image

// Parameter xs = image X axis size, ys = image Y axis size, quality = JPEG Image Quality
Void savecurscreenjpg (lpcwstr pszfilename, int XS, int ys, int quality)

{
Hwnd =: getdomaintopwindow ();
HDC = getwindowdc (null );
Int x = getdevicecaps (HDC, horzres );
Int y = getdevicecaps (HDC, vertres );
Hbitmap hbmp =: createcompatiblebitmap (HDC, x, y), hold;
HDC hmemdc =: createcompatibledc (HDC );
Hold = (hbitmap): SelectObject (hmemdc, hbmp );
Bitblt (hmemdc, 0, 0, x, y, HDC, 0, 0, srccopy );
SelectObject (hmemdc, hold );

Bitmap bit (XS, ys), bit2 (hbmp, null );
Graphics g (& bit );
G. scaletransform (float) XS/X, (float) YS/y );
G. drawimage (& bit2, 0, 0 );

CLSID encoderclsid;
Encoderparameters;

Encoderparameters. Count = 1;
Encoderparameters. Parameter [0]. guid = encoderquality;
Encoderparameters. Parameter [0]. type = encoderparametervaluetypelong;
Encoderparameters. Parameter [0]. numberofvalues = 1;
Encoderparameters. Parameter [0]. value = & quality;

Getencoderclsid (L "image/JPEG", & encoderclsid );
Bit. Save (pszfilename, & encoderclsid, & encoderparameters );

: Deleteobject (hbmp );
: Deleteobject (hmemdc );
Return;
}