也许，你需要理解两个概念，一个是内存位图，这相当于一张图纸，比如A1的大图，它绘图总视野总是从左上角开始，到右下角;另一个概念是视野，可能因为图太大，你的视野不能一眼看全整张图，每次视野总是在图上的某个局部，这个视野就是窗口，窗口是实际可见的区域。如果你在内存绘图后，那么使用Bitblt函数，可以简便的控制希望的视野范围BitBlt The BitBlt function performs a bit-block transfer of the color data corresponding to a rectangle of pixels from the specified source device context into a destination device context. BOOL BitBlt( HDC hdcDest, // handle to destination device context int nXDest, // x-coordinate of destination rectangle's upper-left // corner int nYDest, // y-coordinate of destination rectangle's upper-left // corner int nWidth, // width of destination rectangle int nHeight, // height of destination rectangle HDC hdcSrc, // handle to source device context int nXSrc, // x-coordinate of source rectangle's upper-left // corner int nYSrc, // y-coordinate of source rectangle's upper-left // corner DWORD dwRop // raster operation code );
Parameters hdcDest Handle to the destination device context. nXDest Specifies the logical x-coordinate of the upper-left corner of the destination rectangle. nYDest Specifies the logical y-coordinate of the upper-left corner of the destination rectangle. nWidth Specifies the logical width of the source and destination rectangles. nHeight Specifies the logical height of the source and the destination rectangles. hdcSrc Handle to the source device context. nXSrc Specifies the logical x-coordinate of the upper-left corner of the source rectangle. nYSrc Specifies the logical y-coordinate of the upper-left corner of the source rectangle. dwRop Specifies a raster-operation code. These codes define how the color data for the source rectangle is to be combined with the color data for the destination rectangle to achieve the final color. The following list shows some common raster operation codes: Value Description BLACKNESS Fills the destination rectangle using the color associated with index 0 in the physical palette. (This color is black for the default physical palette.) DSTINVERT Inverts the destination rectangle. MERGECOPY Merges the colors of the source rectangle with the specified pattern by using the Boolean AND operator. MERGEPAINT Merges the colors of the inverted source rectangle with the colors of the destination rectangle by using the Boolean OR operator. NOTSRCCOPY Copies the inverted source rectangle to the destination. NOTSRCERASE Combines the colors of the source and destination rectangles by using the Boolean OR operator and then inverts the resultant color. PATCOPY Copies the specified pattern into the destination bitmap. PATINVERT Combines the colors of the specified pattern with the colors of the destination rectangle by using the Boolean XOR operator. PATPAINT Combines the colors of the pattern with the colors of the inverted source rectangle by using the Boolean OR operator. The result of this operation is combined with the colors of the destination rectangle by using the Boolean OR operator. SRCAND Combines the colors of the source and destination rectangles by using the Boolean AND operator. SRCCOPY Copies the source rectangle directly to the destination rectangle. SRCERASE Combines the inverted colors of the destination rectangle with the colors of the source rectangle by using the Boolean AND operator. SRCINVERT Combines the colors of the source and destination rectangles by using the Boolean XOR operator. SRCPAINT Combines the colors of the source and destination rectangles by using the Boolean OR operator. WHITENESS Fills the destination rectangle using the color associated with index 1 in the physical palette. (This color is white for the default physical palette.) Return Values If the function succeeds, the return value is nonzero.If the function fails, the return value is zero. Windows NT: To get extended error information, callGetLastError. Res If a rotation or shear transformation is in effect in the source device context, BitBlt returns an error. If other transformations exist in the source device context (and a matching transformation is not in effect in the destination device context), the rectangle in the destination device context is stretched, compressed, or rotated as necessary. If the color formats of the source and destination device contexts do not match, the BitBlt function converts the source color format to match the destination format. When an enhanced metafile is being recorded, an error occurs if the source device context identifies an enhanced-metafile device context. Not all devices support the BitBlt function. For more information, see the RC_BITBLT raster capability entry in the GetDeviceCaps function as well as the following functions: MaskBlt, PlgBlt, StretchBlt. BitBlt returns an error if the source and destination device contexts represent different devices. ICM: No color management is performed when blits occur. Windows CE: In Windows CE version 1.0, the dwRop parameter can only be assigned the following values:SRCCOPYSRCANDSRCPAINT SRCINVERT In Windows CE version 2.0, the dwRop parameter can be any ROP3.
也许，你需要理解两个概念，一个是内存位图，这相当于一张图纸，比如A1的大图，它绘图总视野总是从左上角开始，到右下角;另一个概念是视野，可能因为图太大，你的视野不能一眼看全整张图，每次视野总是在图上的某个局部，这个视野就是窗口，窗口是实际可见的区域。如果你在内存绘图后，那么使用Bitblt函数，可以简便的控制希望的视野范围BitBlt
The BitBlt function performs a bit-block transfer of the color data corresponding to a rectangle of pixels from the specified source device context into a destination device context. BOOL BitBlt(
HDC hdcDest, // handle to destination device context
int nXDest, // x-coordinate of destination rectangle's upper-left
// corner
int nYDest, // y-coordinate of destination rectangle's upper-left
// corner
int nWidth, // width of destination rectangle
int nHeight, // height of destination rectangle
HDC hdcSrc, // handle to source device context
int nXSrc, // x-coordinate of source rectangle's upper-left
// corner
int nYSrc, // y-coordinate of source rectangle's upper-left
// corner
DWORD dwRop // raster operation code
);
Parameters
hdcDest
Handle to the destination device context.
nXDest
Specifies the logical x-coordinate of the upper-left corner of the destination rectangle.
nYDest
Specifies the logical y-coordinate of the upper-left corner of the destination rectangle.
nWidth
Specifies the logical width of the source and destination rectangles.
nHeight
Specifies the logical height of the source and the destination rectangles.
hdcSrc
Handle to the source device context.
nXSrc
Specifies the logical x-coordinate of the upper-left corner of the source rectangle.
nYSrc
Specifies the logical y-coordinate of the upper-left corner of the source rectangle.
dwRop
Specifies a raster-operation code. These codes define how the color data for the source rectangle is to be combined with the color data for the destination rectangle to achieve the final color.
The following list shows some common raster operation codes: Value Description
BLACKNESS Fills the destination rectangle using the color associated with index 0 in the physical palette. (This color is black for the default physical palette.)
DSTINVERT Inverts the destination rectangle.
MERGECOPY Merges the colors of the source rectangle with the specified pattern by using the Boolean AND operator.
MERGEPAINT Merges the colors of the inverted source rectangle with the colors of the destination rectangle by using the Boolean OR operator.
NOTSRCCOPY Copies the inverted source rectangle to the destination.
NOTSRCERASE Combines the colors of the source and destination rectangles by using the Boolean OR operator and then inverts the resultant color.
PATCOPY Copies the specified pattern into the destination bitmap.
PATINVERT Combines the colors of the specified pattern with the colors of the destination rectangle by using the Boolean XOR operator.
PATPAINT Combines the colors of the pattern with the colors of the inverted source rectangle by using the Boolean OR operator. The result of this operation is combined with the colors of the destination rectangle by using the Boolean OR operator.
SRCAND Combines the colors of the source and destination rectangles by using the Boolean AND operator.
SRCCOPY Copies the source rectangle directly to the destination rectangle.
SRCERASE Combines the inverted colors of the destination rectangle with the colors of the source rectangle by using the Boolean AND operator.
SRCINVERT Combines the colors of the source and destination rectangles by using the Boolean XOR operator.
SRCPAINT Combines the colors of the source and destination rectangles by using the Boolean OR operator.
WHITENESS Fills the destination rectangle using the color associated with index 1 in the physical palette. (This color is white for the default physical palette.) Return Values
If the function succeeds, the return value is nonzero.If the function fails, the return value is zero. Windows NT: To get extended error information, callGetLastError. Res
If a rotation or shear transformation is in effect in the source device context, BitBlt returns an error. If other transformations exist in the source device context (and a matching transformation is not in effect in the destination device context), the rectangle in the destination device context is stretched, compressed, or rotated as necessary. If the color formats of the source and destination device contexts do not match, the BitBlt function converts the source color format to match the destination format. When an enhanced metafile is being recorded, an error occurs if the source device context identifies an enhanced-metafile device context. Not all devices support the BitBlt function. For more information, see the RC_BITBLT raster capability entry in the GetDeviceCaps function as well as the following functions: MaskBlt, PlgBlt, StretchBlt. BitBlt returns an error if the source and destination device contexts represent different devices. ICM: No color management is performed when blits occur. Windows CE: In Windows CE version 1.0, the dwRop parameter can only be assigned the following values:SRCCOPYSRCANDSRCPAINT SRCINVERT In Windows CE version 2.0, the dwRop parameter can be any ROP3.