GetDeviceCaps查询设备上下文的属性

msdn:https://msdn.microsoft.com/en-us/library/dd144877(VS.85).aspx

GetDeviceCaps用于按照整数索引查询设备上下文的属性，如帧缓冲区格式，色彩处理能力、分辨率、调色板、物理大小、页边距、alpha混合和渐进填充的能力、对ICM的支持，以及DDI特性和限制。

int GetDeviceCaps( _In_ HDC hdc, _In_ int nIndex);

参数：

hdc [in]: 设备上下文的句柄

nIndex [in]:设备上下文的属性索引

The item to be returned. This parameter can be one of the following values.

IndexMeaning

DRIVERVERSION

驱动器版本,16位,格式为0xXYZZ，如0x4001，其中X是操作系统的主版本号，Y是操作系统的次版本号,ZZ是驱动程序的版本号，由驱动程序报告

TECHNOLOGY

Device technology. It can be any one of the following values.

DT_PLOTTER     用于绘图仪

DT_RASDISPLAY     用于光栅显卡

DT_RASPRINTER    用于光栅打印机

DT_RASCAMERA    用于光栅照相机

DT_CHARSTREAM 用于纯设备字体驱动程序

DT_METAFILE   图元文件

DT_DISPFILE    显示器

如果hdc参数指定文件的设备上下文环境，则设备技术就是给CreateEnhMetaFile函数的引用设备，使用GetObjectType函数可以确定它是否是一增强文件设备上下文环境。

HORZSIZE

物理屏幕的宽度(毫米)

VERTSIZE

物理屏幕的高度（毫米）

HORZRES

屏暮的宽度（像素）

VERTRES

屏幕的高度（像素）

LOGPIXELSX

沿屏幕宽度每逻辑英寸的像素数，在多显示器系统中，该值对所显示器相同；

LOGPIXELSY

沿屏幕高度每逻辑英寸的像素数，在多显示器系统中，该值对所显示器相同；

BITSPIXEL

素相连颜色位数

PLANES

颜色位面数

NUMBRUSHES

设备指定画刷数

NUMPENS

设备指定笔数

NUMFONTS

设备指定字体数

NUMCOLORS

设备颜色表的入口数

ASPECTX

用于画线的设备像素的相对宽度

ASPECTY

用于画线的设备像素的相对高度

ASPECTXY

用于画线的设备像素的对角线宽度

PDEVICESIZE

Reserved.

CLIPCAPS

Flag that indicates the clipping capabilities of the device. If the device can clip to a rectangle, it is 1. Otherwise, it is 0.

SIZEPALETTE

Number of entries in the system palette. This index is valid only if the device driver sets the RC_PALETTE bit in the RASTERCAPS index and is available only if the driver is compatible with 16-bit Windows.

NUMRESERVED

Number of reserved entries in the system palette. This index is valid only if the device driver sets the RC_PALETTE bit in the RASTERCAPS index and is available only if the driver is compatible with 16-bit Windows.

COLORRES

Actual color resolution of the device, in bits per pixel. This index is valid only if the device driver sets the RC_PALETTE bit in the RASTERCAPS index and is available only if the driver is compatible with 16-bit Windows.

PHYSICALWIDTH

For printing devices: the width of the physical page, in device units. For example, a printer set to print at 600 dpi on 8.5-x11-inch paper has a physical width value of 5100 device units. Note that the physical page is almost always greater than the printable area of the page, and never smaller.

PHYSICALHEIGHT

For printing devices: the height of the physical page, in device units. For example, a printer set to print at 600 dpi on 8.5-by-11-inch paper has a physical height value of 6600 device units. Note that the physical page is almost always greater than the printable area of the page, and never smaller.

PHYSICALOFFSETX

For printing devices: the distance from the left edge of the physical page to the left edge of the printable area, in device units. For example, a printer set to print at 600 dpi on 8.5-by-11-inch paper, that cannot print on the leftmost 0.25-inch of paper, has a horizontal physical offset of 150 device units.

PHYSICALOFFSETY

For printing devices: the distance from the top edge of the physical page to the top edge of the printable area, in device units. For example, a printer set to print at 600 dpi on 8.5-by-11-inch paper, that cannot print on the topmost 0.5-inch of paper, has a vertical physical offset of 300 device units.

VREFRESH

For display devices: the current vertical refresh rate of the device, in cycles per second (Hz).

A vertical refresh rate value of 0 or 1 represents the display hardware's default refresh rate. This default rate is typically set by switches on a display card or computer motherboard, or by a configuration program that does not use display functions such as ChangeDisplaySettings.

SCALINGFACTORX

Scaling factor for the x-axis of the printer.

SCALINGFACTORY

Scaling factor for the y-axis of the printer.

BLTALIGNMENT

Preferred horizontal drawing alignment, expressed as a multiple of pixels. For best drawing performance, windows should be horizontally aligned to a multiple of this value. A value of zero indicates that the device is accelerated, and any alignment may be used.

SHADEBLENDCAPS

Value that indicates the shading and blending capabilities of the device. See Remarks for further comments.

SB_CONST_ALPHAHandles theSourceConstantAlpha member of theBLENDFUNCTION structure, which is referenced by the blendFunction parameter of theAlphaBlend function.

SB_GRAD_RECTCapable of doingGradientFill rectangles.

SB_GRAD_TRICapable of doingGradientFill triangles.

SB_NONEDevice does not support any of these capabilities.

SB_PIXEL_ALPHACapable of handling per-pixel alpha inAlphaBlend.

SB_PREMULT_ALPHACapable of handling premultiplied alpha inAlphaBlend.

 

RASTERCAPS

Value that indicates the raster capabilities of the device, as shown in the following table.

RC_BANDINGRequires banding support.

RC_BITBLTCapable of transferring bitmaps.

RC_BITMAP64Capable of supporting bitmaps larger than 64 KB.

RC_DI_BITMAPCapable of supporting theSetDIBits andGetDIBits functions.

RC_DIBTODEVCapable of supporting theSetDIBitsToDevice function.

RC_FLOODFILLCapable of performing flood fills.

RC_PALETTESpecifies a palette-based device.

RC_SCALINGCapable of scaling.

RC_STRETCHBLTCapable of performing theStretchBlt function.

RC_STRETCHDIBCapable of performing theStretchDIBits function.

 

CURVECAPS

Value that indicates the curve capabilities of the device, as shown in the following table.

CC_NONEDevice does not support curves.

CC_CHORDDevice can draw chord arcs.

CC_CIRCLESDevice can draw circles.

CC_ELLIPSESDevice can draw ellipses.

CC_INTERIORSDevice can draw interiors.

CC_PIEDevice can draw pie wedges.

CC_ROUNDRECTDevice can draw rounded rectangles.

CC_STYLEDDevice can draw styled borders.

CC_WIDEDevice can draw wide borders.

CC_WIDESTYLEDDevice can draw borders that are wide and styled.

 

LINECAPS

Value that indicates the line capabilities of the device, as shown in the following table:

LC_NONEDevice does not support lines.

LC_INTERIORSDevice can draw interiors.

LC_MARKERDevice can draw a marker.

LC_POLYLINEDevice can draw a polyline.

LC_POLYMARKERDevice can draw multiple markers.

LC_STYLEDDevice can draw styled lines.

LC_WIDEDevice can draw wide lines.

LC_WIDESTYLEDDevice can draw lines that are wide and styled.

 

POLYGONALCAPS

Value that indicates the polygon capabilities of the device, as shown in the following table.

PC_NONEDevice does not support polygons.

PC_INTERIORSDevice can draw interiors.

PC_POLYGONDevice can draw alternate-fill polygons.

PC_RECTANGLEDevice can draw rectangles.

PC_SCANLINEDevice can draw a single scanline.

PC_STYLEDDevice can draw styled borders.

PC_WIDEDevice can draw wide borders.

PC_WIDESTYLEDDevice can draw borders that are wide and styled.

PC_WINDPOLYGONDevice can draw winding-fill polygons.

 

TEXTCAPS

Value that indicates the text capabilities of the device, as shown in the following table.

TC_OP_CHARACTERDevice is capable of character output precision.

TC_OP_STROKEDevice is capable of stroke output precision.

TC_CP_STROKEDevice is capable of stroke clip precision.

TC_CR_90Device is capable of 90-degree character rotation.

TC_CR_ANYDevice is capable of any character rotation.

TC_SF_X_YINDEPDevice can scale independently in the x- and y-directions.

TC_SA_DOUBLEDevice is capable of doubled character for scaling.

TC_SA_INTEGERDevice uses integer multiples only for character scaling.

TC_SA_CONTINDevice uses any multiples for exact character scaling.

TC_EA_DOUBLEDevice can draw double-weight characters.

TC_IA_ABLEDevice can italicize.

TC_UA_ABLEDevice can underline.

TC_SO_ABLEDevice can draw strikeouts.

TC_RA_ABLEDevice can draw raster fonts.

TC_VA_ABLEDevice can draw vector fonts.

TC_RESERVEDReserved; must be zero.

TC_SCROLLBLTDevice cannot scroll using a bit-block transfer. Note that this meaning may be the opposite of what you expect.

 

COLORMGMTCAPS

Value that indicates the color management capabilities of the device.

CM_CMYK_COLORDevice can accept CMYK color space ICC color profile.

CM_DEVICE_ICMDevice can perform ICM on either the device driver or the device itself.

CM_GAMMA_RAMPDevice supportsGetDeviceGammaRamp andSetDeviceGammaRamp

CM_NONEDevice does not support ICM.

 

 

Return value

The return value specifies the value of the desired item.

When nIndex is BITSPIXEL and the device has 15bpp or 16bpp, the return value is 16.