GB2622187A - Image processing method suitable for use with ground marking machines - Google Patents

Abstract

A computer-implemented method of processing an image formed of a plurality of pixels. The method comprises the steps of: receiving an image to be printed ‘S1’; receiving a specification of the number of colours (n) to be used in the print ‘S2’; processing every pixel in the image to identify foreground and background pixels ‘S3’; and classifying all foreground pixels into (n) groups corresponding to the (n) colours and then assigning each foreground pixel a colour from one of the (n) colours ‘S4’. Each of the background pixels may be assigned a background colour of the (n) colours ‘S5’. Classifying the foreground pixels may comprise counting the number of foreground pixels of each colour value and ranking the (n) commonest values in order of frequency. The method may be implemented on an autonomous surface marking machine which may comprise a chassis on a ground wheel arrangement with a nozzle array on a traverse guide movable relative to the ground wheel arrangement such an area can be printed while the machine is stationary.

Description

IMAGE PROCESSING METHOD SUITABLE FOR USE WITH GROUND MARKING MACHINES

The present invention relates to an Autonomous Ground Marking Machine and the like, of a type equipped to deposit materials such as an ink and paint, but may equally deposit sand, seed, fertiliser, or other ground treatments onto a ground surface or for injection under pressure into a ground surface. Such autonomous Machines may be completely autonomous (i.e. free from human operation and/or supervision) or may require at least partial human operation and/or supervision depending on the application.

Background

Ground marking is typically carried out manually. It requires significant pre-planning, the manufacture of pre-ordered plastic stencils, and large teams of workers to decipher instructions, prepare, lay out, and complete a site for marking. Where marking is required such as for logos, safety or hazard signs, the complex make-up of these images means that difficulties persist to print any image, any size, any colour, directly onto any ground surface without significant cost of time, expense and compromise in image attributes such as resolution.

The creative industry from marketers and designers through to the print industry all recognise that artwork files need to be created with the correct resolution and document size. For example, mobile phones or computer monitors use a resolution of 72 Dpi (Dots Per Inch) in RGB (Red, green and Blue). These dots are more commonly known as pixels and printed media normally uses the resolution of 300dpi in CMYK (Cyan, Magenta, Yellow & Black) for publications, such as leaflets or posters Each pixel holds further information regarding its colour, for example one red pixel in a CMYK format will be made up from percentages of the CMYK breakdown. For example, Cyan 0%, Magenta 98%, Yellow 98% and Black 0%. In a typical 6 colour printing press this red colour is then achieved as it passes through each colour on the press. The better the pixel resolution will then achieve closer colour matches to the original artwork.

Anti-aliasing is the smoothing of jagged edges in digital images by averaging the colours of the pixels at a boundary. In gaming for example, anti-aliasing smooths out that jagged appearance of objects caused by low resolution images by blending the edge of a pixel with the adjacent colours and thus providing a better visual appearance.

In conventional printing, the colour of such blurred pixels is interpreted as a combination of multiple colours and the multiple colours can be overlaid to achieve the interpreted colour. Prior art manual ground printing is either performed in a single colour or in the case of more than one colour, different stencils are used for applying different colour layers. In autonomous or semi-autonomous ground printing, only certain colours are carried on the machine.

However, when using anti-aliasing on coloured images, such as a brand's logo, the pixel colours that result along the outer edges of an object can result in quite varied shades. Even colour shades not even used in the original main part of the image or logo before the anti-aliasing is applied. In some ground printing applications, such as those disclosed in this application and in the Applicant's other patents, these edge extra shades are unwanted.

Summary of Invention

According to a first aspect of the present invention, there is provided a computer- implemented method of processing an image formed of a plurality of pixels, the computer-implemented method comprising the steps of: receiving an image to be printed; receiving a specification of the number of colours (n) to be used in the print; processing every pixel in the image to identify foreground and background pixels; and classifying all foreground pixels into (n) groups corresponding to the (n) colours and then assigning each foreground pixel a colour from one of the (n) colours.

Preferably further comprising the step of assigning all the background pixels a background colour, wherein the background colour is one of the (n) colours. Further preferably wherein the step of classifying the foreground pixels into (n) groups corresponding to the (n) colours and then assigning each foreground pixel a colour from one of the (n) colours further comprises the step of counting the number of foreground pixels of each colour value; and then rank the (n) commonest values in order of frequency.

Also preferably wherein the step of classifying the foreground pixels into (n) groups corresponding to the (n) colours and then assigning each foreground pixel a colour from one of the (n) colours, further comprises the step of using a clustering algorithm to classifying the foreground pixels into the (n) groups.

According to a second aspect of the present invention, there is provided a method of printing an image comprising: processing the image using the method of the first aspect; and then generating instructions to print the image.

According to a third aspect of the present invention, there is provided a surface marking autonomous machine comprising: at least one colourant receptacle to hold a colourant material; at least one deposition arrangement; a locomotion arrangement, a control unit, the control unit controlling the least one deposition arrangement and the locomotion means to autonomously deposit the colourant material onto a surface; and wherein the control unit processes an image to print in accordance with the method of the first aspect.

Preferably, wherein the control unit is also operable to process an image to print in accordance with the method of the second aspect.

Further preferably, also comprising a chassis on a ground wheel arrangement with a nozzle array on a traverse guide, the traverse guide permitting movement of the nozzle array beyond the width of the ground wheel arrangement.

Also preferably, wherein the traverse guide is fixed in relation to the ground wheel arrangement. Further preferably, wherein the traverse guide is movable relative to the ground wheel arrangement in the direction of travel, so that an area can be printed while the ground wheel arrangement is stationary.

Preferably, wherein the robot is configured with a nozzle array to print an image or logo on a surface, the robot housing two or more flexible bags containing a material for deposition, the material for deposition contained within each flexible bag being an ink or paint selected from a cyan, magenta, yellow, black, white green, blue or red colour, the image or logo optionally being an advertising logo, design or safety warning.

Thus, there is provided a software method of pre-processing an image in preparation for printing. By determining the intended colour of each pixel in an image, a printing apparatus can print with precision and potentially greater speed. Through this invention, multiple colours of an image can be printed simultaneously and autonomously.

Thus, whilst applicable to wider applications, this invention is particularly relevant to ground printing, in that colours intended for a particular image are pre-mixed and that the image is intended to be printed in only the pre-mixed colours.

List of Figures Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a robot comprising an array of primary packaging comprising bags filled with a ground marking material; Figure 2 is a schematic diagram of primary packaging comprising a flexible ink bag with a hose connected to a nozzle array; Figures 3a and 3b are plan views of a ground marking robot; Figure 4 is a side elevation of a ground marking robot; Figure 5 is a plan view of a ground marking operation in progress, in this embodiment tiled printing of a logo; Figures 6a & 6b are examples of before and after anti-aliasing has been used on an image, as known in the art; and in Figure 7, is a process diagram showing the steps of a method to process anti-aliased images which can be for ground printing applications, according to one embodiment of the present invention The present techniques will be described more fully hereinafter with reference to the accompanying drawings. Like numbers refer to like elements throughout. Parts of the autonomous ground printer are not necessarily to scale and may just be representative of components of the ground print machines, or other described entities.

Detailed Description

The present techniques will be described more fully hereinafter with reference to the accompanying drawings. Like numbers refer to like elements throughout.

Referring to Figure 1 a schematic diagram of an autonomous ground marking robot 10 comprises an outer case 12 cut away to reveal an array of primary packaging 14, 16, 18 and 20. The primary packaging 14, 16, 18 and 20 shown here comprises ink held within a bag (not shown in Figure 1), with primary packaging 14 comprising a red ink R, a green ink G, a blue ink B and a white ink W. Each primary packaging 14, 16, 18 and 20 is supported on a weight measuring plate 14a, 16a, 18a and 20a connected to a smart communications module 22, which may also serve as or be connected to an on-board control system (not shown in Figure 1). The smart communications module 22 comprises a transceiver 22a for communication with remote resources (not shown in Figure 1) Each weight measuring plate 14a, 16a, 18a and 20a is an integral part of a frame 26 capable of holding the primary packaging 14, 16, 18, 20 firmly in place and comprises a load sensor 28 for registering the presence of the primary packaging 14, 16, 18, 20 when firmly in place in the frame 26. Load sensor 28 may be a photodiode or a RFID tag that communicates with an ID tag 30 of the primary packaging 14, 16, 18, 20. ID tag 30 may also comprise a barcode or other smart label, which is used for identification of the primary packaging 14, 16, 18, 20.

As best seen in Figure 2, a flexible ink bag 32 comprises an airtight valve outlet 34 sealed to the flexible ink bag 32, with the appropriate connection part for secure connection to a hose 36. The hose 36 may also be a tube, piping or any suitable means to transport the material for deposition.

The autonomous ground marking robot 10 comprises wheels 24 for movement, a position sensor 38 and laser 40. Position sensor 38 may comprises a Global Positioning Device for navigation or the autonomous ground marking robot 10 may use triangulation with known positioning reflectors and the laser 40 for positioning. In operation, the autonomous ground marking robot 10 may be in constant communication with a positioning device and may reposition itself based on communication from a Global Positioning Device.

Turning to Figure 2, the primary packaging 14 comprising the flexible ink bag 32 with the hose 36 is connected to a nozzle array 42 via an actuator pump 35. Here the nozzle array 42 acts as the means to deposit the material for deposition. Any such suitable nozzle, nozzle array or means to deposit the material, depending on the actual material to be deposited, may be used. Each ink bag of the primary packaging 14, 16, 18 and 20 of Figure 1 will have a hose 36 and valve 34 to connect to the nozzle array 42 via the actuator pump 35. The system may have a single actuator pump 35 for all primary packaging/ink bag/hose (14,16,18,20/32/36), or there may be multiple actuator pumps, i.e. one for each primary packaging/ink bags/hose (14,16,18,20/32/36). Each nozzle of the nozzle array 42 may be designated for each primary packaging/ink bag/hose (14,16,18,20/32/36) present, so that each nozzle is for deposition of only the material held in each primary packing/ink bag (14,16,18,20/32).

In operation, the nozzle array 42 can deposit materials from each primary packing/ink bag (14,16,18,20/32) individually, or multiple nozzles of an array 42 can operate to blend materials together, e.g. colours of inks or paints, to deposit at the same time. The bags 32 may contain different colours of marking materials, i.e. inks or paints, which may comprise CYM or, if good black is required, CYMK colours. Since the substrate or ground to have these deposited upon will not likely be white, a white may be required for any print that has white or a paler shade than the colours contained in the bags 32. When depositing ink or paint to print an image, the image may be printed in sweeps to generate small adjacent dots (i.e. each dot comes from a single nozzle of the array 42), and when viewed from above or a suitable distance from afar (e.g. from the stand in a stadium or from a television view) appear to blend into colours, depending on the relative colours of the different inks or colours deposited. In the present embodiment, the flexible ink bag 32 comprises the red ink R suitable for depositing a red colour on a ground.

In operation, a user receives a package containing primary packaging 14 as a lightweight, substantially rigid cardboard box containing therein a flexible bag 32 filled with a ground marking material, for example a red ink R. The user may register the marking material using the ID tag 30 to match marking materials held in a database by way of communication with smart communications module 22.

The sensor 28 may register the presence of the primary packaging 14 and further verify that the correct ink bag 32 is located in the correct frame and may further undertake a verified check of the authenticity of the ink bag 32 using RFID technology or measurement from the weight monitoring plate 14a.

The hose 36 is attached to the valve 34 and with appropriate setting up of the autonomous ground marking robot as best described in Figures 3a, 3b, 4 and 5, printing or marking can commence.

Figures 3a and 3b are plan views of the autonomous ground marking robot 10, 3a is a top view, 3b is an underneath view, Figure 4 is a side elevation and Figure 5 is a plan view of a ground marking operation in progress, in this embodiment the tiled printing of a logo.

The ground printer 10 comprises the case 12 held securely by a chassis supporting the ground wheel arrangement 24 with a print head 60 on a traverse guide 62, the traverse guide 62 permitting movement of the print head 60 beyond the width W of the ground wheel arrangement 24, along the length of the print width 68. The nozzle array 42 as described above may be attached to the print head 60. The nozzles maybe fixed and the print head 60 moveable. The print head 60, via the print guide 62, may be moveable along the length of a print width 68, which is the area the print head is capable of printing.

The ground wheel arrangement 24 comprises wheels 24a, 24b, 24c and 24d to steer the autonomous ground marking robot 10 along a path to affect the printing, and this may be under the control of a print file that can be loaded into the on-board control system, such as may be contained communications module 22. The traverse guide 62 is fixed in relation to the ground wheel arrangement 24, so that it prints one line of an image along the print width 68. The ground wheel arrangement 24 then notches forward, moving the whole printer 10 forward for it to print another line.

The wheel arrangement 24 may have independent drives to manage torque for optimised positioning accuracy on any surface. The independent drives may be connected to the smart communications module 22 to feedback into drive control. The autonomous ground marking robot 10 may be able to respond in real time to changing terrain needs.

As shown in Figure 6a, the section of line on the left is aliased. The section of a line on the right (Figure 613) has had anti-aliasing applied to make the edges appear smoother, wherein anti-aliasing is the smoothing of jagged edges in digital images by averaging the colours of the pixels at a boundary.

As explained previously, when using anti-aliasing on coloured images, such as a brand's logo, the pixel colours that result along the outer edges of an object can result in quite varied shades. Even colour shades not even used in the original main part of the image or logo before the anti-aliasing is applied. In some ground printing applications, such as those disclosed in this application and in the Applicant's other patents, these edge shades are unwanted. This is because when the image is printed on the ground, such as a football pitch, 'random' shades of colours can be deposited. And when seen by a blind eye, these random pixels can stand out, as counter to the intention of anti-a liasing, they do not blend into the image.

As such, there is shown in Figure 7, a description of a method to process anti-aliased images which can be for ground printing applications, according to one embodiment of the present invention.

Start of Process Si: Upload the image to be printed to the machine (as described with reference to Figures 1 to 5, alternatively to software located in the cloud, which processes the image and sends the results, as print instructions, to the machine).

52. Specify the number of colours to be used in the Print (n) and their colour values 53 Process every pixel in print to identify foreground and background pixels. This can be done using many techniques, as known in the art.

54 For all foreground pixels, process and assign one of the (n) colours using the following steps: i) count the number of pixels of each colour value; H) then rank the (n) commonest values in order of frequency; iii) then use a clustering algorithm to classify the pixels into one of the top (n) groups; and iv) then assign each foreground pixel a new colour value from one of the (n) colours.

55: For all background pixels, assign background pixels the background colour (which in grass printing is usually transparent, so no paint is deposited at all for background pixels. However, as this technique may be used in other application, this step is included for completeness).

End of Process Thus, a software method is described for the pre-processing an image in preparation for printing. The software looks at each pixel of the image and determine to which one of a plurality of predetermined colours each pixel belongs (e.g. if a logo is in white and blue, whether a pixel should be white or blue). In particular, in an image, a border between multiple colours can be blurred and pixels near the border can appear a different colour from, or a combination of, the intended colours.

By determining the intended colour of each pixel in an image, a printing apparatus can print with precision and potentially greater speed, whilst removing the possibility of a random blue pixel appearing in a swathe of a mainly white colour, for example.

The robots, systems, and methods described herein can be adapted for use with different surfaces, such as sports (e.g. football, cricket, racing, rugby, hockey, ice hockey, skiing, shooting) pitches, race courses, indoor sports venues and running tracks. In examples, the material for deposition is a herbicide, pesticide, insecticide, plant growth aid, water or marking material, optionally wherein the marking material is a paint, chemical, coloured material, powder. The robots and method of using such robots described herein may also carry out multiple functions at the same time. For example, bags may contain paint for deposition to mark a logo on a pitch and may also contain fertiliser to fertilise the pitch.

It will be clear to one skilled in the art that many improvements and modifications can be made to the foregoing exemplary embodiments without departing from the scope of the present technique.

Claims (11)

1. Claims: 1 A computer-implemented method of processing an image formed of a plurality of pixels, the computer-implemented method comprising the steps of: i) receiving an image to be printed; H) receiving a specification of the number of colours (n) to be used in the print; Hi) processing every pixel in the image to identify foreground andbackground pixels; andiv) classifying all foreground pixels into (n) groups corresponding to the (n) colours and then assigning each foreground pixel a colour from one of the (n) colours.
2. 2. A computer-implemented method according to claim 1, further comprising the step of assigning all the background pixels a background colour, wherein the background colour is one of the (n) colours.
3. 3 A computer-implemented method according to claim 1 or 2, wherein the step of classifying the foreground pixels into (n) groups corresponding to the (n) colours and then assigning each foreground pixel a colour from one of the (n) colours further comprises the step of counting the number of foreground pixels of each colour value; and then rank the (n) commonest values in order of frequency.
4. 4. A computer-implemented method according to claim 3, wherein the step of classifying the foreground pixels into (n) groups corresponding to the (n) colours and then assigning each foreground pixel a colour from one of the (n) colours, further comprises the step of using a clustering algorithm to classifying the foreground pixels into the (n) groups.
5. 5. A method of printing an image comprising: processing the image using the method of any of claims 1 to 4; and then generating instructions to print the image.
6. 6 A surface marking autonomous machine comprising: at least one colourant receptacle to hold a colourant material; at least one deposition arrangement; a locomotion arrangement, a control unit, the control unit controlling the least one deposition arrangement and the locomotion means to autonomously deposit the colourant material onto a surface; and wherein the control unit processes an image to print in accordance with the method of any of claims 1 to 4.
7. 7. A surface marking autonomous machine according to claim 6, wherein the control unit processes an image to print in accordance with the method of claim 5.
8. 8. A surface marking autonomous machine as claimed in claims 6 or], further comprising a chassis on a ground wheel arrangement with a nozzle array on a traverse guide, the traverse guide permitting movement of the nozzle array beyond the width of the ground wheel arrangement.
9. 9. A surface marking autonomous machine according to claim 8, in which the traverse guide is fixed in relation to the ground wheel arrangement.
10. 10. A surface marking autonomous machine according to claim 9, in which the traverse guide is movable relative to the ground wheel arrangement in the direction of travel, so that an area can be printed while the ground wheel arrangement is stationary.
11. 11. A surface marking autonomous machine as claimed in any of claims 6 to 10, wherein the robot is configured with a nozzle array to print an image or logo on a surface, the robot housing two or more flexible bags containing a material for deposition, the material for deposition contained within each flexible bag being an ink or paint selected from a cyan, magenta, yellow, black, white green, blue or red colour, the image or logo optionally being an advertising logo, design or safety warning.