Documentation
¶
Overview ¶
Package raster implements a decoder for the CUPS raster format. It provides functions for decoding a CUPS raster stream line-wise or page-wise.
For a list of currently supported color spaces and bit depths, see the documentation of Page.ParseColors.
Index ¶
- Constants
- Variables
- type BoundingBox
- type CUPSBoundingBox
- type CUPSHeader
- type Decoder
- type Header
- type Page
- func (p *Page) LineSize() int
- func (p *Page) ParseColors(b []byte) ([]color.Color, error)
- func (p *Page) ReadAll(b []byte) error
- func (p *Page) ReadAllColors(b []byte) ([]color.Color, error)
- func (p *Page) ReadLine(b []byte) error
- func (p *Page) ReadLineColors(b []byte) ([]color.Color, error)
- func (p *Page) Size() int
- func (p *Page) UnreadLines() int
Constants ¶
const ( AdvanceNever = 0 AdvanceAfterFile = 1 AdvanceAfterJob = 2 AdvanceAfterSet = 3 AdvanceAfterPage = 4 )
const ( CutNever = 0 CutAfterFile = 1 CutAfterJob = 2 CutAfterSet = 3 CutAfterPage = 4 )
const ( JogNever = 0 JogAfterFile = 1 JogAfterJob = 2 JogAfterSet = 3 )
const ( EdgeTop = 0 EdgeRight = 1 EdgeBottom = 2 EdgeLeft = 3 )
const ( RotateNone = 0 RotateCounterClockwise = 1 RotateUpsideDown = 2 RotateClockwise = 3 )
const ( ChunkyPixels = 0 BandedPixels = 1 PlanarPixels = 2 )
const ( ColorSpaceGray = 0 ColorSpaceRGB = 1 ColorSpaceRGBA = 2 ColorSpaceBlack = 3 ColorSpaceCMY = 4 ColorSpaceYMC = 5 ColorSpaceCMYK = 6 ColorSpaceYMCK = 7 ColorSpaceKCMY = 8 ColorSpaceKCMYcm = 9 ColorSpaceGMCK = 10 ColorSpaceGMCS = 11 ColorSpaceWHITE = 12 ColorSpaceGOLD = 13 ColorSpaceSILVER = 14 ColorSpaceCIEXYZ = 15 ColorSpaceCIELab = 16 ColorSpaceRGBW = 17 ColorSpacesGray = 18 ColorSpacesRGB = 19 ColorSpaceAdobeRGB = 20 ColorSpaceICC1 = 32 ColorSpaceICC2 = 33 ColorSpaceICC3 = 34 ColorSpaceICC4 = 35 ColorSpaceICC5 = 36 ColorSpaceICC6 = 37 ColorSpaceICC7 = 38 ColorSpaceICC8 = 39 ColorSpaceICC9 = 40 ColorSpaceICCA = 41 ColorSpaceICCB = 42 ColorSpaceICCC = 43 ColorSpaceICCD = 44 ColorSpaceICCE = 45 ColorSpaceICCF = 46 ColorSpaceDevice1 = 48 ColorSpaceDevice2 = 49 ColorSpaceDevice3 = 50 ColorSpaceDevice4 = 51 ColorSpaceDevice5 = 52 ColorSpaceDevice6 = 53 ColorSpaceDevice7 = 54 ColorSpaceDevice8 = 55 ColorSpaceDevice9 = 56 ColorSpaceDeviceA = 57 ColorSpaceDeviceB = 58 ColorSpaceDeviceC = 59 ColorSpaceDeviceD = 60 ColorSpaceDeviceE = 61 ColorSpaceDeviceF = 62 )
Variables ¶
var ( // ErrUnknownVersion is returned when encountering an unknown // magic byte sequence. It is indicative of input in a newer // format, or input that isn't a CUPS raster stream at all. ErrUnknownVersion = errors.New("unsupported file format or version") // ErrUnsupported is returned when encountering an unsupported // feature. This includes unsupported color spaces, color // orderings or bit depths. ErrUnsupported = errors.New("unsupported feature") // ErrBufferTooSmall is returned from ReadLine and ReadAll when // the buffer is smaller than Page.LineSize or Page.Size // respectively. ErrBufferTooSmall = errors.New("buffer too small") // ErrInvalidFormat is returned when encountering values that // aren't possible in the supported versions of the format. ErrInvalidFormat = errors.New("error in the format") )
Functions ¶
This section is empty.
Types ¶
type CUPSBoundingBox ¶
type CUPSHeader ¶
type CUPSHeader struct {
// v1
Width int
Height int
MediaType int
BitsPerColor int
BitsPerPixel int
BytesPerLine int
ColorOrder int
ColorSpace int
Compression int
RowCount int
RowFeed int
RowStep int
// v2, v3
NumColors int
BorderlessScalingFactor float32
PageSize [2]float32
ImagingBBox CUPSBoundingBox
Integer [16]int
Real [16]float32
String [16]string
MarkerType string
RenderingIntent string
PageSizeName string
}
type Header ¶
type Header struct {
MediaClass string
MediaColor string
MediaType string
OutputType string
AdvanceDistance int
AdvanceMedia int
Collate bool
CutMedia int
Duplex bool
HorizDPI int
VertDPI int
BoundingBox BoundingBox
InsertSheet bool
Jog int
LeadingEdge int
MarginLeft int
MarginBottom int
ManualFeed bool
MediaPosition int
MediaWeight int
MirrorPrint bool
NegativePrint bool
NumCopies int
Orientation int
OutputFaceUp bool
Width int
Length int
Separations bool
TraySwitch bool
Tumble bool
CUPS CUPSHeader
}
type Page ¶
type Page struct {
Header *Header
// contains filtered or unexported fields
}
func (*Page) ParseColors ¶
ParseColors parses b and returns the colors stored in it, one per pixel.
It currently supports the following color spaces and bit depths, although more might be added later:
- 1-bit, ColorSpaceBlack -> color.Gray
- 8-bit, ColorSpaceBlack -> color.Gray
- 8-bit, ColorSpaceCMYK -> color.CMYK
Note that b might contain data for more colors than are actually present. This happens when data is stored with less than 8 bits per pixel. A page with 633 pixels per line would necessarily contain data for 640 pixels, as pixels 633-640 are stored in the same byte. When parsing ReadLine data, make sure to truncate the returned slice to the length of a single line. When parsing ReadAll data, the stride with which the resulting slice of colors is accessed has to be rounded up. Alternatively, ReadLineColors and ReadAllColors may be used, which return slices of colors and truncate them as needed.
func (*Page) ReadAll ¶
ReadAll reads the entire page into b. If ReadLine has been called previously, ReadAll will read the remainder of the page. It returns io.EOF if the entire page has been read already.
func (*Page) ReadAllColors ¶
ReadAllColors reads the page and returns the color for each pixel. Unlike using ReadAll and ParseColors, this function will not return more values than there are pixels in a page. b is used as scratch space and must be at least p.Header.CUPSBytesPerLine bytes large.
func (*Page) ReadLine ¶
ReadLine returns the next line of pixels in the image. It returns io.EOF if no more lines can be read. The buffer b must be at least p.Header.CUPSBytesPerLine bytes large.
func (*Page) ReadLineColors ¶
ReadLineColors reads a line and returns the color for each pixel. Unlike using ReadLine and ParseColors, this function will not return more values than there are pixels in a line. b is used as scratch space and must be at least p.Header.CUPSBytesPerLine bytes large.
func (*Page) UnreadLines ¶
UnreadLines returns the number of unread lines in the page.
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