Abstract: Examples relate to image processing, and performing fixed length format cell compression on a cell of a planar colour image based on an amount of white colour of the cell, the cell comprising a plurality of pixels, to obtain a compressed cell having four or fewer colour levels; and performing variable length format cell compression on the compressed cell to obtain a coded compressed cell.

Abstract: An example apparatus is for printing to a substrate. The example apparatus comprises a printing fluid device and an air flow device. The printing fluid device is for transferring printing fluid to a substrate. The air flow device is to create an air curtain so that any printing fluid residue from the transfer of the printing fluid to the substrate is at least partially prevented from migrating toward a user of the apparatus.

Abstract: In an example, a method includes measuring a temperature of a plurality of regions of a layer of build material in an additive manufacturing apparatus to provide initial temperature values. For each of a plurality of regions which comprise build material which is intended to fuse, an average temperature value of a plurality of neighbouring regions may be determined and the initial temperature values may be replaced with the average temperature value. Based on the replacement temperature values, a representative temperature of an area of the layer of build material may be determined and a heat source may be controlled based on the representative temperature.

Abstract: In an example, a method includes measuring a temperature of a plurality of regions of a layer of build material in an additive manufacturing apparatus to provide initial temperature values. For each of a plurality of regions which comprise build material which is intended to fuse, an average temperature value of a plurality of neighbouring regions may be determined and the initial temperature values may be replaced with the average temperature value. Based on the replacement temperature values, a representative temperature of an area of the layer of build material may be determined and a heat source may be controlled based on the representative temperature.

Abstract: In an example, a method includes acquiring, at a processor, a first data model and a second data model. The first data model comprises a representation of at least one property of at least part of a first object and the second data model comprises a representation of at least one property of at least part of a second object. The first and second objects are to be generated in a common additive manufacturing operation. The method may include generating a first print layer model and a second, different, print layer model using the processor by combining at least parts of the first data model and the second data model and generating additive manufacturing instructions based on the first print layer model and the second print layer model.

Abstract: A number of colors in a predefined region of an image to be compressed are determined. The predefined region has a plurality of pixels. In response to determining that the number of colors is greater than a first predefined threshold, a lossy compression process is selected dependent on a number of pixels in the predefined region having a predefined color. The selected lossy compression process is applied to the predefined region.

Abstract: An example method includes acquiring a model of an object to be generated in three-dimensional object generation which is segmented into a plurality of object model sub-volumes, each sub-volume representing a region of the object which is individually addressable in object generation. Object model sub-volumes within a first depth of an object model surface are defined at a first resolution and object model sub-volumes beyond the first depth are defined at a second resolution, and the first resolution is a higher resolution than the second resolution. An object generation model is applied to the object model to determine at least one predicted dimensional deviation of the object in object generation. A geometric adjustment to the segmented object model may be determined to compensate for the predicted dimensional deviation by adding and/or removing at least one object model sub-volume defined at the first resolution.

Abstract: A method of recirculating fluid in a printhead die is provided. The recirculation is performed for at least one nozzle, such that the recirculation finishes before the corresponding at least one nozzle completed ejection of a drop.

Abstract: In an example, a method includes receiving a first data model of an object to be generated in additive manufacturing, at a processor. Using the processor, a second data model may be determined. Determining the second data model may include generating for each of plurality of contiguous, non-overlapping sub-volumes of a volume containing the object, a sub-volume octree characterising the sub-volume and having a root node. Determining the second data model may further include generating a volume octree characterising the volume containing the object, the volume octree characterising in its lowest nodes the root nodes of the sub-volume octrees.

Abstract: In an example, an image processing system may include an identification engine, a map engine, and a control engine. In that example, the identification engine may identify a color mapping resource in response to a classification identifier corresponding to image data, the map engine may map the image data with the color mapping resource having color space clause corresponding to the classification identifier, and the control engine may generate control data for operating a print apparatus to print based on the color mapping resource.

Abstract: In an example, a method includes receiving, at a processor, data representing at least part of an object to be manufactured in a layer-by-layer manufacturing process. A serialised octree representation of at least part of the object may be generated from the data. In the serialised octree representation, nodes are ordered such that (i) a node representing a volume which includes a layer of the object to be generated earlier in an intended order of object generation precedes a node representing a volume which consists of layer(s) of the object to be generated subsequently; (ii) nodes representing a volume which includes a given layer of the object are ordered based on a level of the nodes within the octree representation, wherein parent nodes appear before descendent nodes; and (iii) nodes representing a volume which includes a given layer of the object and being of the same level within the octree representation are ordered according to a location encoding pattern.

Abstract: A method of recirculating fluid in a printhead die is provided. The method comprises generating ejection data specifying a nozzle of the printhead from which a drop is to be ejected and storing the ejection data in a first memory. Recirculation data is generated for the nozzle for which a recirculation operation is to be performed, and the recirculation data is stored in a second memory different from the first memory. Fluid is recirculated in the nozzle on the basis of the recirculation data in advance of ejecting a drop from the nozzle on the basis of the ejection data. The recirculation data is generated based on the respective ejection data for the nozzle.

Abstract: A method comprises receiving object model data in an original coordinate system to print within a predefined usable build volume of a three dimensional printer. The method comprises receiving at least one compensation factor for the object model data to compensate for any shrinking of an object. The method comprises scaling the object model data by the at least one compensation factor to provide printable object model data. The scaling is performed with reference to an origin at a centre of the usable build volume.

Abstract: A method of recirculating fluid in a printhead die is provided. The recirculation is performed for at least one nozzle, such that the recirculation finishes before the corresponding at least one nozzle completed ejection of a drop.

Abstract: In some examples herein, control data is for application of treatment fluid on a treatment substrate location surrounding a substrate dot corresponding to a first pixel of the digital image. Treatment fluid is ejected on the treatment substrate location if a metric value computed from pixel values of a set of pixels in the neighborhood of the first pixel is above a threshold level.

Abstract: In some examples, an imaging device may include a controller including processing circuitry to detect, a first quantity of rows of pixels to be included as a first band of a contone image, process the pixels of each row of the first band in parallel raster order, detect a second quantity of rows of pixels to be included as a second band of the contone image; and process the pixels of each row of the second band in response to the completion of the pixels of the first band, where the rows of the second band are processed in parallel in serpentine order with respect to the first band.

Abstract: In an example, a method includes receiving, at a processor, data representing a three dimensional object. Using the processor, a modified data representation of the three dimensional object may be determined wherein, in the modified data representation, the three dimensional object is represented in terms of homogenous sub-volumes. Each homogenous sub-volume is homogenous with respect to a predetermined attribute and contains locations which are within a common object boundary distance band of plurality of object boundary distance bands, wherein at least two object boundary distance bands partially overlap.

Abstract: According to an example, an apparatus may include a processor and a memory. The memory may have stored thereon machine readable instructions that may cause the processor to access an initial halftone image of a three-dimensional (3D) object, the initial halftone image being generated from a continuous tone image of the 3D object. The instructions may also cause the processor to iteratively modify voxel data for the initial halftone image to identify updated voxel data that more accurately corresponds to the continuous tone image than the initial halftone image and to generate halftone image printing data for the 3D object containing the updated voxel data.

Abstract: In an example, a method includes receiving a first data model of an object to be generated in additive manufacturing, at a processor. Using the processor, a second data model may be determined. Determining the second data model may include generating for each of plurality of contiguous, non-overlapping sub-volumes of a volume containing the object, a sub-volume octree characterising the sub-volume and having a root node. Determining the second data model may further include generating a volume octree characterising the volume containing the object, the volume octree characterising in its lowest nodes the root nodes of the sub-volume octrees.

Abstract: A method of recirculating fluid in a printhead die is provided. The method comprises generating ejection data specifying a nozzle of the printhead from which a drop is to be ejected and storing the ejection data in a first memory. Recirculation data is generated for the nozzle for which a recirculation operation is to be performed, and the recirculation data is stored in a second memory different from the first memory. Fluid is recirculated in the nozzle on the basis of the recirculation data in advance of ejecting a drop from the nozzle on the basis of the ejection data. The recirculation data is generated based on the respective ejection data for the nozzle.