The hottest printer color management

2022-09-27
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Printer color management (middle)

12.2.2 driver control and device control

if color management control is provided by the driver or printer hardware, the printer graphics DLL of the driver must set gcaps in the DEVINFO structure_ ICM marking

the driver must indicate the support for CYMK color space (if the sample tooling with shoulder end and rib end is suitable), as described in the section supporting CMYK color space

the printer graphics DLL must define the following three functions:

drvicmcreatecolortransform

drvicmdeletecolortransform

drvicmccheckbitmapbits

GDI calls the drvicmcreatecolortransform function and provides it to the printer driver with ICC profile (described in the SDK document of the platform). Given these profiles, functions can create an internal color transformation to be used when correcting color information. Color transformation is a specific driver, which internally defines the mapping from one color space to another. Function returns a handle to the transform and is stored by GDI

marks in the brushobj and xlateobj structures indicate whether color management is performed by the system (or application) or by the driver (or device). When each driver implements a DDI drawing function that receives one or all functions, the tag must also be checked. If the application in the system is currently handling color management, the driver or device will not. If the driver or device color management is allowed, the DDI function must call brushjobj_ Hgetcolortransform or xlateobj_ Hgetcolortransform function

handle proprietary color management

for some devices, whether ICM has been allowed or not, proprietary color management is implemented (through driver or hardware). Drivers of these devices are not allowed to perform color correction whether ICM has been allowed or not. Color correction is not allowed when the image data received by the driver of these devices has been modified. The pre modified data can be received if:

■ an application has an image "outside the DC" with color modification (refer to the SDK document of the platform) in addition to affecting the misalignment of the jaws

■ color management is handled by the system

for either of these two cases, the br of the flcolortype member in brushobj_ HOST_ ICM tag and XO of flxlate member in xlateobj_ HOST_ ICM flag must be set. Even the dmicmmethod member of DevMode is set to dmicmmethod_ When none, these marks can also be set

12.2.3 support CMYK color space

whether a color management is handled by an application, system, driver or device, a printer graphics DLL must indicate whether it supports CMYK color space. This is caused by setting gcaps in the DEVINFO structure_ Cmykcolor tag. If this flag is set and CMYK's profiles file is used, GDI sends CMYK color data to printer graphics DLL instead of RGB data for bitmap, brush and pen, but I am confident in the potential of this kind of material. GDI also sets the following flags:

■ br in the flcolortype member in the brushobj structure_ Cmykcolor tag

■ XO in flxlate member in xlateobj structure_ FROM_ CMYK tag

note that if the driver supports CMYK color space, it must also support transitional color matching. In this way, if the driver sets gcaps in the DEVINFO structure_ Cmykcolor flag, which must also set gcaps_ Halftone tag

12.2.4 color management of JPEG and PNG images

for printers that provide hardware JPEG and PNG compressed image support, color management must be handled by drivers or devices, not GDI. This equipment is specially designed for the power line zigzag experiment according to the requirements of GB4706, IEC60335, ul859:4.2, ul1005:3.9 and other standard terms, aiming at the variety and different shapes of home appliance products.

before the application sends JPEG or PNG compressed images to the printer, it will call extescape with the sequence code of checkjpegformat or checkpngformat. This will result in a call to the drvquerydevicesupport function of the driver with a query type of QDs_ Checkjpegformat or QDs_ Checkpngformat and a buffer contain compressed data

The

driver can check the image data and decide whether it can support the image. If XO of xlateobj structure_ DEVICE_ ICM mark or XO_ HOST_ When the ICM flag is set, the supported images must perform color conversion, because GDI cannot perform color conversion on these images

for these compressed images, the color space information is usually contained in the image data. An exception is the JFIF file, which is encoded by YCbCr, and for it, the default sRGB space is a good approximation. However, a JFIF file may contain a proprietary appx tag that specifies the color space, in which case the driver must convert the image using the color space

for more data about supporting JPEG and PNG compressed images, refer to the comments section of DEVINFO in DDK

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