Subgroup: Raster

Class: QgsRasterBlock

class qgis.core.QgsRasterBlock

Bases: sip.wrapper

QgsRasterBlock(dataType: Qgis.DataType, width: int, height: int) Constructor which allocates data block in memory

Parameters:
  • dataType – raster data type
  • width – width of data matrix
  • height – height of data matrix

QgsRasterBlock(QgsRasterBlock)

Raster data container.

Methods

applyNoDataValues
applyScaleOffset Apply band scale and offset to raster block values
color Read a single color
convert Convert data to different type.
data Gets access to raw data.
dataType Returns data type
dataTypeSize
error Returns the last error
hasNoData Returns true if the block may contain no data.
hasNoDataValue True if the block has no data value.
height Returns the height (number of rows) of the raster block.
image Returns an image containing the block data, if the block’s data type is color.
isEmpty Returns true if block is empty, i.e.
isNoData Check if value at position is no data
isValid Returns true if the block is valid (correctly filled with data).
noDataValue Returns no data value.
printValue Print double value with all necessary significant digits.
reset Reset block
resetNoDataValue Reset no data value: if there was a no data value previously set, it will be discarded.
setColor Set color on position
setData Rewrite raw pixel data.
setError Sets the last error
setImage Sets the block data via an image.
setIsData Remove no data flag on pixel.
setIsNoData Set no data on pixel
setIsNoDataExcept Set the whole block to no data except specified rectangle
setNoDataValue Sets cell value that will be considered as “no data”.
setValid Mark block as valid or invalid
setValue Set value on position
subRect For extent and width, height find rectangle covered by subextent.
toString
typeIsColor Returns true if data type is color
typeIsNumeric Returns true if data type is numeric
typeSize
typeWithNoDataValue For given data type returns wider type and sets no data value
value Read a single value if type of block is numeric.
valueBytes Gets byte array representing a value.
width Returns the width (number of columns) of the raster block.

Signals

Attributes

applyNoDataValues(self, rangeList: object)
applyScaleOffset(self, scale: float, offset: float)

Apply band scale and offset to raster block values

New in version 2.3.

color(self, row: int, column: int) → int

Read a single color

Parameters:
  • row – row index
  • column – column index
Returns:

color *

color(self, index: int) -> int Read a single value

Parameters:index – data matrix index (long type in Python)
Returns:color *
convert(self, destDataType: Qgis.DataType) → bool

Convert data to different type.

Parameters:destDataType – dest data type
Returns:true on success *
data(self) → QByteArray

Gets access to raw data. The returned QByteArray instance is not a copy of the data: it only refers to the array owned by the QgsRasterBlock, therefore it is only valid while the QgsRasterBlock object still exists. Writing to the returned QByteArray will not affect the original data: a deep copy of the data will be made and only the local copy will be modified.

Note

in Python the method returns ordinary bytes object as the

New in version 3.0.

dataType(self) → Qgis.DataType

Returns data type

dataTypeSize(self) → int
error(self) → QgsError

Returns the last error

hasNoData(self) → bool

Returns true if the block may contain no data. It does not guarantee that it really contains any no data. It can be used to speed up processing. Not the difference between this method and hasNoDataValue().

Returns:true if the block may contain no data *
hasNoDataValue(self) → bool

True if the block has no data value.

Returns:true if the block has no data value

See also

noDataValue()

height(self) → int

Returns the height (number of rows) of the raster block.

See also

width()

New in version 2.10.

image(self) → QImage

Returns an image containing the block data, if the block’s data type is color.

isEmpty(self) → bool

Returns true if block is empty, i.e. its size is 0 (zero rows or cols). This method does not return true if size is not zero and all values are ‘no data’ (null).

isNoData(self, row: int, column: int) → bool

Check if value at position is no data

Parameters:
  • row – row index
  • column – column index
Returns:

true if value is no data *

isNoData(self, row: int, column: int) -> bool Check if value at position is no data

Parameters:
  • row – row index
  • column – column index
Returns:

true if value is no data *

isNoData(self, index: int) -> bool Check if value at position is no data

Parameters:index – data matrix index (long type in Python)
Returns:true if value is no data *
isValid(self) → bool

Returns true if the block is valid (correctly filled with data). An empty block may still be valid (if zero size block was requested). If the block is not valid, error may be retrieved by error() method.

noDataValue(self) → float

Returns no data value. If the block does not have a no data value the returned value is undefined.

Returns:No data value

See also

hasNoDataValue()

printValue(value: float) → str

Print double value with all necessary significant digits. It is ensured that conversion back to double gives the same number.

Parameters:value – the value to be printed
Returns:string representing the value*
reset(self, dataType: Qgis.DataType, width: int, height: int) → bool

Reset block

Parameters:
  • dataType – raster data type
  • width – width of data matrix
  • height – height of data matrix
Returns:

true on success

resetNoDataValue(self)

Reset no data value: if there was a no data value previously set, it will be discarded.

See also

noDataValue()

New in version 3.0.

setColor(self, row: int, column: int, color: int) → bool

Set color on position

Parameters:
  • row – row index
  • column – column index
  • color – the color to be set, QRgb value
Returns:

true on success *

setColor(self, index: int, color: int) -> bool Set color on index (indexed line by line)

Parameters:
  • index – data matrix index (long type in Python)
  • color – the color to be set, QRgb value
Returns:

true on success *

setData(self, data: Union[QByteArray, bytes, bytearray], offset: int = 0)

Rewrite raw pixel data. If the data array is shorter than the internal array within the raster block object, pixels at the end will stay untouched. If the data array is longer than the internal array, only the initial data from the input array will be used. Optionally it is possible to set non-zero offset (in bytes) if the input data should overwrite data somewhere in the middle of the internal buffer.

New in version 3.0.

setError(self, error: QgsError)

Sets the last error

setImage(self, image: QImage) → bool

Sets the block data via an image.

Returns:true on success
setIsData(self, row: int, column: int)

Remove no data flag on pixel. If the raster block does not have an explicit no data value set then an internal map of no data pixels is maintained for the block. In this case it is possible to reset a pixel to flag it as having valid data using this method. This method has no effect for raster blocks with an explicit no data value set.

Parameters:
  • row – row index
  • column – column index

New in version 2.10.

setIsData(self, index: int) Remove no data flag on pixel. If the raster block does not have an explicit no data value set then an internal map of no data pixels is maintained for the block. In this case it is possible to reset a pixel to flag it as having valid data using this method. This method has no effect for raster blocks with an explicit no data value set.

Parameters:index – data matrix index (long type in Python)

New in version 2.10.

setIsNoData(self, row: int, column: int) → bool

Set no data on pixel

Parameters:
  • row – row index
  • column – column index
Returns:

true on success *

setIsNoData(self, index: int) -> bool Set no data on pixel

Parameters:index – data matrix index (long type in Python)
Returns:true on success *

setIsNoData(self) -> bool Set the whole block to no data

Returns:true on success *
setIsNoDataExcept(self, exceptRect: QRect) → bool

Set the whole block to no data except specified rectangle

Returns:true on success *
setNoDataValue(self, noDataValue: float)

Sets cell value that will be considered as “no data”.

See also

noDataValue()

New in version 3.0.

setValid(self, valid: bool)

Mark block as valid or invalid

setValue(self, row: int, column: int, value: float) → bool

Set value on position

Parameters:
  • row – row index
  • column – column index
  • value – the value to be set
Returns:

true on success *

setValue(self, index: int, value: float) -> bool Set value on index (indexed line by line)

Parameters:
  • index – data matrix index (long type in Python)
  • value – the value to be set
Returns:

true on success *

subRect(extent: QgsRectangle, width: int, height: int, subExtent: QgsRectangle) → QRect

For extent and width, height find rectangle covered by subextent. The output rect has x oriented from left to right and y from top to bottom (upper-left to lower-right orientation).

Parameters:
  • extent – extent, usually the larger
  • width – numbers of columns in theExtent
  • height – numbers of rows in theExtent
  • subExtent – extent, usually smaller than theExtent
Returns:

the rectangle covered by sub extent

toString(self) → str
typeIsColor(type: Qgis.DataType) → bool

Returns true if data type is color

typeIsNumeric(type: Qgis.DataType) → bool

Returns true if data type is numeric

typeSize(dataType: int) → int
typeWithNoDataValue(dataType: Qgis.DataType) → Tuple[Qgis.DataType, float]

For given data type returns wider type and sets no data value

value(self, row: int, column: int) → float

Read a single value if type of block is numeric. If type is color, returned value is undefined.

Parameters:
  • row – row index
  • column – column index
Returns:

value *

value(self, index: int) -> float Read a single value if type of block is numeric. If type is color, returned value is undefined.

Parameters:index – data matrix index (long type in Python)
Returns:value *
valueBytes(dataType: Qgis.DataType, value: float) → QByteArray

Gets byte array representing a value.

Parameters:
  • dataType – data type
  • value – value
Returns:

byte array representing the value *

width(self) → int

Returns the width (number of columns) of the raster block.

See also

height()

New in version 2.10.