Classifications

• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
  • G06T11/00—2D [Two Dimensional] image generation
  • G06T11/001—Texturing; Colouring; Generation of texture or colour

Definitions

• the present invention relates generally to the processing of digitized images in a computer network environment, in particular client-server.
• a client computer user wishes to view an image available on a server computer
• this image is downloaded to the client computer via the network.
• It can be, for example, an image in millions of colors, with a depth of 24 bits per pixel, and known processing (for example according to the JPEG standard) makes it possible to transmit this image in compressed form, with the aim in particular minimize the transfer time and the space required for its storage, both on the server and client sides.
• JPEG standard for example according to the JPEG standard
• the server site must include storage memories which can be considerable to be able to store all these images.
• the server needs in terms of bandwidth are important, due to the need to transmit, with each new request from a client station, the entire image requested.
• the object of the present invention is to propose a method and a system for displaying an image on a client station which, in certain contexts, make it possible to remedy these drawbacks.
• the present invention proposes, according to a first aspect, a method of displaying an image on a display device of a data processing equipment, characterized in that it comprises the following steps:
• the choice step is carried out in a table having several entries, each containing predefined color or texture data.
• - Said table is transferred from the server system to the data equipment during the transfer step (c).
• the choice step is carried out from a choice list displayed on a display device of the data processing equipment, the number of which is equal to the number of entries in said table.
• the choice step is carried out from a palette of colors displayed on a display device of the data processing equipment, and the method further comprises a step consisting in determining which of the entries of said table corresponds as close as possible to one or more colors chosen by the user.
• the determination step consists in combining differences between the hue, saturation and brightness values of a color chosen by the user, and of an imposed color contained in each entry of the said table.
• the determination step comprises the search for a minimum difference value (e) between the chosen color and the colors defined at the various entries of the table, the difference being each time determined according to the following formula:
• the method further comprises, before the determination step, a step of converting the values of red, green and blue of the color chosen by the user and of the color defined at each entry of the table into said values hue, saturation and shine.
• - Said mask comprises a plurality of zones capable of being modified individually, and the steps of choosing colors and building the new image are carried out for each of said zones.
• the mask has the format of an image with a depth of N bits, said areas being distributed in the depth of the image, and the size of the mask is equal to the size of the original image.
• each of the N bits associated with each pixel of the mask defines a mask layer.
• each possible value of the bytes of N bits associated with each pixel of the mask defines a mask layer.
• one of the mask layers defines an area of pixels of the image which must not be modified.
• the mask has, at least for its transfer, the format of a plurality of images without depth, which define the respective areas and at least some of which have a size less than _. that of the starting image and are defined by two dimensions and coordinates of an origin point.
• the invention provides a data processing system, comprising a central processing unit, memories and a display device, as well as a means of communication with a data server, said system comprising:
• processing means for placing in said zone or in each zone the chosen color or a color derived from the chosen color.
• reception means are also able to receive from said data server, in association with said image and said mask, a table of color constraints
• said processing means are able to place in said zone or in each zone only one color contained in said color constraint table.
• the processing means are able to place in said zone the color directly chosen in the table by the user.
• the processing means comprise means for determining a difference between a color chosen by the user and colors contained in the color constraint table, and are able to place the color having the slightest difference with respect to the color chosen in the associated area.
• the deviation determination means are capable of calculating a difference between colors according to the following formula:
• the processing means are capable of developing a color value derived from a color chosen in using brightness information from the starting image in the area concerned.
• FIG. 1 illustrates a representation of colors in the RGB format
• FIG. 2 illustrates a representation of colors in the HSB format
• FIG. 3 is a diagram illustrating a process for changing image colors according to the present invention.
• the present invention can be implemented for example in a client station constituted by a standard computer of the "PC" type, which will not be described here, this client station being able to connect, for example via the telephone network and the Internet, at any data server station.
• a client station constituted by a standard computer of the "PC" type, which will not be described here, this client station being able to connect, for example via the telephone network and the Internet, at any data server station.
• the purpose of a local application of colors and / or textures in accordance with the present invention is to allow one or more users of client stations connected to a server station via a network to view an image coming from the server station according to a arbitrary or predefined number of variations of colors and / or textures applied to one or more areas of the original image, without having to reload an image each time from the server station.
• the definition of the individually modifiable zones is carried out by means of a second image, called image mask, which is transmitted to the client station concerned at the same time as the original image.
• the application of colors can be carried out by the user either freely, by choosing one or more colors from any palette of colors available to him on his workstation, or in a constrained manner, that is to say restricted to a set given colors or associated color sets, which is also transmitted to the client station from the server station at the same time as the original image and the image mask, and which contains a table of data of color constraints defining different colors or different sets of colors which are authorized to be associated respectively with the different areas of the image defined by the mask; in the latter case, means may be provided in the client station for choosing, from the palette available on his station, the color closest to the color defined by the color constraint data, according to a color search method such as 'will be described in detail below.
• a color search method such as 'will be described in detail below.
• Color models The color models used are:
• This model separates the colors into 3 main components, red, green and blue, Perfectly suited for computer screens with cathode ray tube, composed of 3 guns representing the same colors, and associated graphics cards.
• the most common model is to represent each pixel in 3 components of 8 bits each, or 24 bits in total, allowing to represent 16 million colors.
• a color is then represented in a 3-dimensional space, as illustrated in Figure 1, and the geometric shape associated with this model is a cube.
• This widely used model is however not very representative of human vision.
• This model breaks down a color into 3 fundamental characteristics.
• the hue is the wavelength reflected or transmitted by an object, and is represented by an angle generally expressed in degrees and between 0 ° and 360 °, with convention
• Red 0 degrees
• Green 120 degrees
• Blue 240 degrees.
• the tint value is normalized, so that the range of variations is between 0 and 1, the value 0 representing 0 °, and the value 1 representing 360 °. Saturation measures the strength of color. It is represented by a percentage between 0 and
• the brightness represents the intensity of light, by a percentage value also between 0% and 100%. At 0%, there is no light, and the color appears black. At 100% the brightness is maximum.
• the geometric shape associated with this model is illustrated in Figure 2 of the drawings. It: appears as a double cone whose main axis is that of shine; the further we move laterally from this axis, the more the color is saturated; finally the angle formed by the projection of the color vector considered in a horizontal plane, with respect to a reference axis contained in this plane, gives the hue value.
• This model is very representative of human vision, and more suitable for the application of algorithms related to color, such as segmentation for example.
• the procedure for changing the colors of an original image in a client computer is carried out in five main steps:
• the program is loaded, for example, during an Internet session, according to the Java language specifications of the American company Sun Microsystems.
• This step is only necessary in the environment of a navigation program for the Internet, or Intranet. In the case of other applications on other types of networks, this step may not exist, the program then being called like any other program on the user's machine.
• the initialization step consists in loading an image I to be modified in the program.
• This image here represents an OB object intended to undergo the color changes.
• the input format for this image can be any; in particular, the image may have been compressed using various techniques (JPEG or Wavelets for example), and it is then decompressed before processing. In this example, it is an image of mxn pixels downloaded via the Internet from a server site.
• bitmap type images typically for images in millions of colors whose color depth is 3 x 8 bits (8 bits per Red, Green and Blue channel), i.e. there is a correspondence between each point of the image and the display on the screen (as opposed to an image of the type vector, where the display is made by applying functions). If an image mask M accompanies image I (which is done by an appropriate link), it is also loaded.
• the input format of the mask M can be any. In this case, it is a bit card type mask, uncompressed or compressed without loss of information so that it can be faithfully restored.
• This image mask M of size identical to the image M to be processed, contains one or more zones without overlapping with each other. The membership of a given point in a region is defined by the value of the pixel at the coordinates of this point. The convention used here is to associate a plane bit with each region, so that, if the mask M is given the same format as a bit map image with a depth of 8 bits, this mask can define eight masking layers Ml, M2, etc. each having one or more zones, the or each zone of the same layer having to be associated with the same color when processing color changes.
• the masking layer M1 contains a zone Zl corresponding to a part of the object OB contained in the image I
• the masking layer M2 contains two zones Z2 and Z2 'corresponding to two other parts of l 'object, these two zones Z2 and Z2' must each time have the same color because they are contained in the same masking layer.
• this format of the mask can be used more finely so as to associate with each value of the byte associated with each pixel a masking layer, so as to thus produce up to 256 masking layers.
• the masking layer associated with the value byte 0 is reserved to designate all the pixels that do not belong to any color change zone. Thus all the points of this layer remain intact during color changes.
• the different zones are defined by individual 1-bit images (black and white) the size of which can be smaller than that of the initial image, in particular if the zone in question is significantly larger. smaller than the whole picture. This part of the mask is then defined by a rectangle of given dimensions and starting from an origin also given.
• the luminances of each zone of the mask are then calculated: thus, for each point of the starting image I, the average luminance is calculated for each region defined by the mask image M. If no mask image M is associated with image I, then the average luminance over the entire image is calculated. The average luminance of a region - or of the whole image - is calculated by adding the brightness values of all the pixels in the area (or of the image), then dividing this sum by the total number of pixels taken into account
• Each entry X in this table consists of n triples, namely a triplet (r X ⁇ , g x ⁇ , b x ⁇ ) per masking layer M ⁇ defined by the mask M, each triplet containing 3 values r x ⁇ , g x ⁇ and b x ⁇ defining in the RGB model the color to be applied in the zone or zones defined by this layer.
• this table once loaded in the buffer serves as a reference.
• This table can be used in different ways.
• the program offers the user, by a menu or any type of list to choose from, the possibility of directly choosing any one from the entries of the table.
• Zone Zl Zones Z2 and Z2 'white light gray light blue dark blue red pink yellow orange
• the method uses the values contained in the considered input of the color constraint table to modify the different zones and reconstruct an image I 'corresponding to the choice, this image then being displayed on the screen.
• the program can be designed to offer the user an initially unconstrained choice of colors for the different zones. Zi.
• This approach will be described in more detail in the case where image I is associated with a single masking layer, with consequently a choice of color unique by the user.
• This choice is made for example using a palette of colors displayed on the screen, in which the user makes a selection using the mouse. Once the user has made this choice, a process is then implemented to calculate the difference between the chosen color and each color in the color constraint table, in order to find the authorized color which is closest to the one requested.
• the nearest color that is to say the one having the minimum difference with the requested color, will then be applied.
• the distance e (Cl, C2) between the two colors Cl and C2 is preferably calculated in the HSB model, that is to say after having converted the RGB triplets from the color constraint table into the HSB format, and after having - if necessary - converted the color requested by the user into this same HSB format.
• the following formula is preferably used:
• the distance on the hue value h which is defined in terms of angle, is calculated odulo 360 °.
• the distance d (hl, h2) is well calculated as being 0.21 and not 0.79.
• Another possibility of the present invention is to allow the user, from a given image I and a given image mask M, but without color constraints in the sense described above, to independently create a image I 'having different colors, essentially chosen freely in the different zones.
• the user's request can be formed for example by direct specification of n RGB triples corresponding to the n areas to be colored, or preferably by means of a graphic interface comprising one or more color palettes in RGB format.
• the first step is to convert the requested triples into HSB format, and to determine from HSB values the values to be applied to the different areas of the image.
• r zone number varying for example from 0 to n-1 Br mean value of the current brightness for all the points in the area Zr Lr brightness value requested by the user.
• the eye is very sensitive to the Bright / dark differences (light and shadow) of the pixels of an area, and it is important to keep for the pixels of the area concerned a distribution of brightness similar to that of the original image.
• B (i, j) B (i, j) if M (i, j) e Zo (no change)
• B (i, j) B (i, j) xPr if M (i, j) e Zr
• the present invention finds application in many fields where variable images must be displayed at a client station after transfer from a server station.
• the present invention allows an efficiency gain in following areas:

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• 1999
  • 1999-07-19 FR FR9909322A patent/FR2797370B1/fr not_active Expired - Fee Related
• 2000
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  • 2000-07-19 EP EP00953260A patent/EP1204951A1/de not_active Withdrawn
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