Method and system for extracting bottom layer of block

Abstract

The invention discloses a method and system for extracting a bottom layer player of a block, and relates to the technical field of data processing, and the method comprises the following steps: obtaining each player of the block, and selecting a player to be extracted; the object in the layer to be extracted is traversed; obtaining top boundary coordinate data of each object; creating an object frame according to the top boundary coordinate data of each object; and adding the object frame body to a top layer player of the block. According to the method and the device, the layer information of the block is obtained, the bottom layer to be extracted is selected from the layer information, the boundary coordinates of the objects in the bottom layer in the top layer are obtained, the object frame is created according to the boundary coordinates and added to the top layer, the object frame does not need to enter a real layer of the layout to carry out manual adding operation, and the accuracy and the execution efficiency of layer extraction are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of data processing, and in particular to a method and system for extracting an underlying layer of a block. Background Art

[0002] When designing a layout, especially when it comes to complex integrated circuit design, there is a need to extract the layer of the bottom block to the top layer, which involves extracting the metal stack or extracting the polysilicon layer. There are many steps in the multi-layer processing of the layout, and it is necessary to ensure that the layer selection and size are correct, and the position of the layer is accurate for precise alignment and matching.

[0003] The existing bottom layer extraction method requires manually creating a rectangle based on the layer information and aligning the rectangle with the top layer; or entering the real layer of the layer, copying the window to the clipboard and pasting it to a new window, and then aligning the pasted window with the top layer. The existing bottom layer extraction method has many steps and relies on the manual operation of the layout designer, which has the problems of misoperation during the execution process and low efficiency of layer extraction. Therefore, an accurate and efficient method for extracting the bottom layer is needed. Summary of the invention

[0004] The purpose of the present invention is to provide a method and system for extracting the bottom layer of a block, by obtaining the layer information of the block and selecting the bottom layer to be extracted, obtaining the boundary coordinates of each object in the bottom layer in the top layer, creating an object frame according to the boundary coordinates and adding it to the top layer, without entering the real layer of the layout for manual addition operations, thereby improving the accuracy and execution efficiency of layer extraction.

[0005] The purpose of the present invention is achieved by the following technical means: In a first aspect, the present invention provides a method for extracting an underlying layer of a block, comprising the following steps: Get each layer of the block and select the layer to be extracted; Traverse the objects in the layer to be extracted; Obtaining top-level boundary coordinate data of each of the objects; Creating an object frame according to the top-level boundary coordinate data of each object; Add the object frame to the top layer of the block.

[0006] Preferably, the obtaining of top-level boundary coordinate data of each of the objects comprises the following steps: Acquire boundary coordinate data of the object; According to the hierarchical structure of the block, obtain the coordinate transformation data of the object; The top-level boundary coordinate data of the object is calculated according to the boundary coordinate data of the object and the coordinate transformation data of the object.

[0007] Preferably, calculating the top-level boundary coordinate data of the object according to the boundary coordinate data of the object and the coordinate transformation data of the object comprises the following steps: Calculating the cumulative translation amount according to the coordinate transformation data; The boundary coordinate data of the object is subjected to coordinate transformation according to the accumulated translation amount to obtain the top-level boundary coordinate data of the object.

[0008] Preferably, creating an object frame according to the top-level boundary coordinate data of each object comprises the following steps: Set the position and size of the extraction range; Sort the abscissa of the top-level boundary coordinate data of each object and the abscissa of the extraction range by size to obtain a abscissa sequence; Obtain two horizontal coordinate data located in the middle of the horizontal coordinate sequence; Sort the ordinates of the top-level boundary coordinate data of each object and the ordinate of the extraction range by size to obtain a ordinate sequence; Obtain two ordinate data located in the middle of the ordinate sequence; The object frame is created according to the horizontal coordinate data and the vertical coordinate data.

[0009] Preferably, setting the position and size of the extraction range comprises the following steps: Selecting a first coordinate point in the layout as the starting point of the extraction range; Recording the coordinate data of the first coordinate point; Selecting a second coordinate point in the layout as the end point of the extraction range; Recording the coordinate data of the second coordinate point; According to the first coordinate point and the second coordinate point, a rectangular frame is created as the extraction range; The position and size of the extraction range are determined according to the coordinate data of the first coordinate point and the coordinate data of the second coordinate point.

[0010] Preferably, before adding the object frame to the top layer of the block, the method further includes the following steps: Performing overlap detection on the object frame; The overlapping object frames are merged.

[0011] In a second aspect, the present invention provides a system for extracting the bottom layer of a block, applying the above-mentioned method for extracting the bottom layer of a block, comprising: a layer information acquisition module, an object data extraction module, a top-level coordinate acquisition module, an object frame creation module and an object frame addition module; The layer information acquisition module is used to obtain each layer of the block and select the layer to be extracted; The object data extraction module is used to traverse the objects in the layer to be extracted; The top-level coordinate acquisition module is used to acquire the top-level boundary coordinate data of each of the objects; The object frame creation module is used to create an object frame according to the top-level boundary coordinate data of each object; The object frame adding module is used to add the object frame to the top layer of the block.

[0012] Preferably, it also includes: an object frame merging module; The object frame merging module is used to perform overlap detection on the object frames and merge the overlapping object frames before adding the object frames to the top layer of the block.

[0013] In a third aspect, the present invention provides an electronic device, comprising a processor and a memory, wherein the memory is used to store computer program code, and the computer program code comprises computer instructions. When the processor executes the computer instructions, the electronic device executes the above-mentioned method of extracting the bottom layer of a block.

[0014] In a fourth aspect, the present invention provides a computer-readable storage medium, wherein a computer program is stored in the computer-readable storage medium. The computer program includes program instructions, and when the program instructions are executed by a processor of an electronic device, the processor executes the above-mentioned method of extracting the underlying layer of a block.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention obtains the layer information of the block and selects the bottom layer to be extracted, obtains the boundary coordinates of each object in the bottom layer in the top layer, creates an object frame according to the boundary coordinates and adds it to the top layer, without entering the real layer of the layout for manual addition operations, thereby improving the accuracy and execution efficiency of layer extraction; The present invention obtains the cumulative translation of each object with respect to the top layer, performs coordinate transformation on the boundary coordinate data of the object to obtain the top boundary coordinate data, and realizes the conversion of the object coordinate system in the bottom layer to the coordinate system of the top layer, thus providing a data basis for the subsequent creation of the object frame to realize the extraction of the bottom layer; The present invention improves the execution efficiency of layer extraction by selecting a first coordinate point and a second coordinate point in a layout, setting the position and size of an extraction range, and selecting an extraction range of an underlying layer according to process requirements; The present invention performs overlap detection on created object frames and merges the overlapping object frames, thereby improving the accuracy of layer extraction. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0018] Figure 1 A flowchart of a method for extracting the bottom layer of a block provided in this embodiment; Figure 2 A schematic diagram of the process of obtaining top-level boundary coordinate data of each object in step S5 provided in this embodiment; Figure 3 A schematic diagram of a flow chart of step S53 provided in this embodiment, which is to calculate the top-level boundary coordinate data of the object according to the boundary coordinate data of the object and the coordinate transformation data of the object; Figure 4 Step S7 provided in this embodiment is a flowchart of creating an object frame according to the top-level boundary coordinate data of each object; Figure 5 A schematic diagram of a flow chart of setting the position and size of the extraction range in step S71 provided in this embodiment; Figure 6 A schematic diagram of the structure of a system for extracting the bottom layer of a block provided in this embodiment; Figure 7 A schematic diagram of the structure of an electronic device provided in this embodiment. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0021] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0022] Embodiment 1 This embodiment provides a method for extracting the underlying layer of a block, such as Figure 1 As shown, the following steps are included: S1, get each layer of the block and select the layer to be extracted; S3, traverse the objects in the layer to be extracted; S5, obtaining top-level boundary coordinate data of each object; S7, creating an object frame according to the top boundary coordinate data of each object; S9, add the object frame to the top layer of the block.

[0023] It should be noted that when drawing a layout, there are multiple blocks in the layout, and each block can contain multiple layers. Each layer has a different structure and is responsible for different functions, such as metal layer M1, metal layer M2, polysilicon layer, etc. Each layer can be regarded as a two-dimensional plane diagram that describes the information of the layer. The objects in the layer are the basic physical elements that constitute the circuit of the layer. The types of objects will also be different according to the different layers, such as contact holes between connecting areas, semiconductor devices, isolation structures of various devices, and routing, etc. This embodiment forms a layer list of the block by obtaining the hierarchical structure of each block and the layer name of the block. The layer list lists the names of the layers in sequence according to the hierarchical structure. By selecting the bottom layer to be extracted in the layer list, obtaining the boundary coordinates of each object of the bottom layer in the top layer, and creating an object frame, the bottom layer is extracted into the top layer.

[0024] In this embodiment, by obtaining the layer information of the block and selecting the bottom layer to be extracted, the boundary coordinates of each object in the bottom layer in the top layer are obtained, and an object frame is created according to the boundary coordinates and added to the top layer. There is no need to enter the real layer of the layout for manual addition operations, which improves the accuracy and execution efficiency of layer extraction.

[0025] In some embodiments, step S5, the top boundary coordinate data of each object is obtained, such as Figure 2 As shown, the following steps are included: S51, obtaining boundary coordinate data of the object; S52, obtaining coordinate transformation data of the object according to the hierarchical structure of the block; S53, calculating the top-level boundary coordinate data of the object according to the boundary coordinate data of the object and the coordinate transformation data of the object.

[0026] It should be noted that for a layout design with a hierarchical structure, the bottom layer needs to consider the position transformation of the upper layer. The upper layer and the lower layer are in a contained relationship, and the lower layer and the objects in the layer are also in a contained relationship. There is a position offset between layers, and objects also have their own positions relative to the layer, which also have position offsets. Therefore, it is necessary to trace the boundary coordinate data of the object upward along the hierarchical path to obtain the coordinate transformation data of the object for the top layer. Based on the coordinate transformation data, the boundary coordinate data of the object in the top layer can be calculated, that is, the real coordinate data of the object.

[0027] Specifically, in some embodiments, step S53 calculates the top-level boundary coordinate data of the object according to the boundary coordinate data of the object and the coordinate transformation data of the object, such as Figure 3 As shown, the following steps are included: S531, calculating the cumulative translation amount according to the coordinate transformation data; S532, performing coordinate transformation on the boundary coordinate data of the object according to the accumulated translation amount to obtain the top-level boundary coordinate data of the object.

[0028] For example, take the layer below the top layer for object extraction. The origin of the coordinate system of the top layer is , the lower layer has moved to a certain position of the top layer, and the real coordinates of the origin of its coordinate system are , and an object in the lower layer also has its own position relative to the lower layer, and its coordinates in the coordinate system of the lower layer are In this case, to get the top-level coordinates of the object, you need to combine the two transformations and calculate the cumulative translation of the object, so that the top-level coordinates of the object are , from which the top boundary coordinate data of all objects can be calculated.

[0029] In this embodiment, by obtaining the cumulative translation of each object with respect to the top layer, the boundary coordinate data of the object is transformed to obtain the top boundary coordinate data, so as to realize the conversion of the object coordinate system in the bottom layer to the coordinate system of the top layer, thereby providing a data basis for the subsequent creation of the object frame to realize the extraction of the bottom layer.

[0030] In some embodiments, step S7 creates an object frame according to the top boundary coordinate data of each object, such as Figure 4 As shown, the following steps are included: S71, setting the position and size of the extraction range; S72, sorting the horizontal coordinates of the top boundary coordinate data of each object and the horizontal coordinates of the extraction range according to the size to obtain a horizontal coordinate sequence; S73, obtaining two horizontal coordinate data in the middle of the horizontal coordinate sequence; S74, sorting the vertical coordinates of the top boundary coordinate data of each object and the vertical coordinates of the extraction range according to their sizes to obtain a vertical coordinate sequence; S75, obtaining two ordinate data in the middle of the ordinate sequence; S76, creating an object frame according to the horizontal coordinate data and the vertical coordinate data.

[0031] In some embodiments, step S71, the position and size of the extraction range are set, such as Figure 5 As shown, the following steps are included: S711, selecting a first coordinate point in the layout as the starting point of the extraction range; S712, recording coordinate data of the first coordinate point; S713, selecting a second coordinate point in the layout as the end point of the extraction range; S714, recording coordinate data of the second coordinate point; S715, creating a rectangular frame as an extraction range according to the first coordinate point and the second coordinate point; S716, determining the position and size of the extraction range according to the coordinate data of the first coordinate point and the coordinate data of the second coordinate point.

[0032] It should be noted that when extracting the layer to be extracted, the object of the entire underlying layer can be extracted, or objects of a partial area can be extracted while meeting the process requirements, thereby reducing the time of layer extraction and improving the efficiency of layer extraction. By selecting the first coordinate point in the layout as the starting point, the coordinate data of the first coordinate point is recorded. , then select the second coordinate point in the layout as the end point, and record the coordinate data of the second coordinate point , so that we can get a coordinate point with a length of , width is The rectangular box is used as the extraction range.

[0033] The top boundary coordinate data of the object and the coordinate data of the extraction range are usually the data of two coordinate points. The position and size of the boundary box are determined by the data of these two coordinate points. Then, the horizontal coordinate sequence obtained by sorting the horizontal coordinate of the top boundary coordinate of the object and the horizontal coordinate of the extraction range includes four horizontal coordinate data, which are two horizontal coordinate data of the top boundary coordinate of the object and two horizontal coordinate data of the extraction range; similarly, the vertical coordinate sequence obtained by sorting the vertical coordinate of the top boundary coordinate of the object and the vertical coordinate of the extraction range includes four vertical coordinate data, which are two vertical coordinate data of the top boundary coordinate of the object and two vertical coordinate data of the extraction range. Remove the largest and smallest horizontal coordinate data in the horizontal coordinate sequence and the largest and smallest vertical coordinate data in the vertical coordinate sequence, and obtain the two horizontal coordinate data and vertical coordinate data in the middle, which are used as the boundary coordinate data of the object frame, and create the corresponding object frame. The object frame obtained in this way can exclude objects outside the extraction range. When the object is outside the extraction range, the object frame obtained is the boundary box of the extraction range; when the object is within the extraction range, the object frame obtained is the top boundary box of the object.

[0034] In this embodiment, by selecting the first coordinate point and the second coordinate point in the layout, setting the position and size of the extraction range, and selecting the extraction range of the bottom layer according to the process requirements, the execution efficiency of the layer extraction is improved.

[0035] In some embodiments, before adding the object frame to the top layer of the block, step S9 further includes the following steps: S81, performing overlap detection on the object frame; S82, merging overlapping object frames.

[0036] It should be noted that there is a partial overlap or complete overlap between the generated object frame and the object frame. At this time, the overlapping object frames can be merged. Exemplarily, the objects in the bottom layer include semiconductor devices and routing lines distributed in the layer. These objects will have a connection relationship. The object frame created according to the top-level boundary coordinate data will have a partial overlap. When it is detected that two object frames overlap, the two object frames are merged. In some embodiments, objects are screened by selecting an extraction range. The object frame obtained by the top-level boundary coordinate data for objects outside the extraction range is the boundary frame of the extraction range. If there are multiple objects outside the extraction range, multiple object frames with the same position and size as the boundary frame of the extraction range will be created. At this time, these overlapping object frames can be merged.

[0037] In this embodiment, overlap detection is performed on the created object frames and the overlapping object frames are merged, thereby improving the accuracy of layer extraction.

[0038] Embodiment 2 This embodiment provides a system for extracting the bottom layer of a block, and applies the above method for extracting the bottom layer of a block, such as Figure 6 As shown, it includes: a layer information acquisition module, an object data extraction module, a top-level coordinate acquisition module, an object frame creation module and an object frame adding module; The layer information acquisition module is used to obtain each layer of the block and select the layer to be extracted; Object data extraction module, used to traverse the objects in the layer to be extracted; A top-level coordinate acquisition module is used to obtain top-level boundary coordinate data of each object; An object frame creation module is used to create an object frame according to the top boundary coordinate data of each object; The object frame adding module is used to add the object frame to the top layer of the block.

[0039] In this embodiment, by obtaining the layer information of the block and selecting the bottom layer to be extracted, the boundary coordinates of each object in the bottom layer in the top layer are obtained, and an object frame is created according to the boundary coordinates and added to the top layer. There is no need to enter the real layer of the layout for manual addition operations, which improves the accuracy and execution efficiency of layer extraction.

[0040] In some embodiments, it further includes: an object frame merging module; The object frame merging module is used to detect overlaps of object frames and merge overlapping object frames before adding them to the top layer of the block. In this embodiment, overlap detection is performed on the created object frames and the overlapping object frames are merged, thereby improving the accuracy of layer extraction.

[0041] It should be understood that the disclosed system can be implemented in other ways. For example, the system embodiments described above are merely schematic. For example, the division of the above modules is only a logical function division. There may be other division methods in actual implementation. For example, multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, each functional module can be integrated into a processing module, or each module can exist physically separately, or two or more modules can be integrated into one module. The above integrated modules can be implemented in the form of hardware or in the form of software functional modules.

[0042] Embodiment 3 This embodiment provides an electronic device 2, such as Figure 7 As shown, a processor 21 and a memory 22, the memory 22 is used to store computer program codes, the computer program codes include computer instructions, when the processor 21 executes the computer instructions, the electronic device executes the above-mentioned method of extracting the bottom layer of the block.

[0043] The electronic device 2 includes a processor 21, a memory 22, an output device 23, and an input device 24. The processor 21, the memory 22, the output device 23, and the input device 24 are coupled via a connector, and the connector includes various interfaces, transmission lines, or buses, etc., which are not limited in the embodiments of the present invention. It should be understood that in various embodiments of the present invention, coupling refers to mutual connection in a specific manner, including direct connection or indirect connection through other devices, for example, through various interfaces, transmission lines, buses, etc.

[0044] The processor 21 may be one or more graphics processing units (GPUs). When the processor 21 is a GPU, the GPU may be a single-core GPU or a multi-core GPU. Optionally, the processor 21 may be a processor group consisting of multiple GPUs, and the multiple processors are coupled to each other via one or more buses. Optionally, the processor 21 may also be other types of processors, etc., which are not limited in the embodiments of the present invention.

[0045] The memory 22 can be used to store computer program instructions and various computer program codes including program codes for executing the scheme of the present invention. Optionally, the memory 22 includes but is not limited to random access memory (RAM), read-only memory (ROM), erasable programmable read only memory (EPROM), or portable read only memory (CD-ROM), and the memory 22 is used for related instructions and data.

[0046] The input device 24 is used to input data and / or signals, and the output device 23 is used to output data and / or signals. The output device 23 and the input device 24 can be independent devices or an integrated device.

[0047] This embodiment provides a computer-readable storage medium, in which a computer program is stored. The computer program includes program instructions. When the program instructions are executed by a processor of an electronic device, the processor executes the above-mentioned method of extracting the bottom layer of a block.

[0048] The above are only specific embodiments of the present invention, which enable those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for extracting the bottom layer of a block, characterized in that: The following steps are involved: Get each layer of the block and select the layer to be extracted; Traverse the objects in the layer to be extracted; Obtaining top-level boundary coordinate data of each of the objects; Creating an object frame according to the top-level boundary coordinate data of each object; Add the object frame to the top layer of the block.

2. A method for extracting the bottom layer of a block according to claim 1, characterized in that: The step of obtaining the top-level boundary coordinate data of each object comprises the following steps: Acquire boundary coordinate data of the object; According to the hierarchical structure of the block, obtain the coordinate transformation data of the object; The top-level boundary coordinate data of the object is calculated according to the boundary coordinate data of the object and the coordinate transformation data of the object.

3. A method for extracting the bottom layer of a block according to claim 2, characterized in that: The step of calculating the top-level boundary coordinate data of the object according to the boundary coordinate data of the object and the coordinate transformation data of the object comprises the following steps: Calculating the cumulative translation amount according to the coordinate transformation data; The boundary coordinate data of the object is subjected to coordinate transformation according to the accumulated translation amount to obtain the top-level boundary coordinate data of the object.

4. The method for extracting the bottom layer of a block according to claim 1, characterized in that: The step of creating an object frame according to the top-level boundary coordinate data of each object comprises the following steps: Set the position and size of the extraction range; Sort the abscissa of the top-level boundary coordinate data of each object and the abscissa of the extraction range by size to obtain a abscissa sequence; Obtain two horizontal coordinate data located in the middle of the horizontal coordinate sequence; Sort the ordinates of the top-level boundary coordinate data of each object and the ordinate of the extraction range by size to obtain a ordinate sequence; Obtain two ordinate data located in the middle of the ordinate sequence; The object frame is created according to the horizontal coordinate data and the vertical coordinate data.

5. A method for extracting the bottom layer of a block according to claim 4, characterized in that: The step of setting the position and size of the extraction range comprises the following steps: Selecting a first coordinate point in the layout as the starting point of the extraction range; Recording the coordinate data of the first coordinate point; Selecting a second coordinate point in the layout as the end point of the extraction range; Recording the coordinate data of the second coordinate point; According to the first coordinate point and the second coordinate point, a rectangular frame is created as the extraction range; The position and size of the extraction range are determined according to the coordinate data of the first coordinate point and the coordinate data of the second coordinate point.

6. The method for extracting the bottom layer of a block according to claim 1, characterized in that: Before adding the object frame to the top layer of the block, the following steps are also included: Performing overlap detection on the object frame; The overlapping object frames are merged.

7. A system for extracting the bottom layer of a block, using the method for extracting the bottom layer of a block as claimed in any one of claims 1 to 6, characterized in that: include: layer information acquisition module, object data extraction module, top-level coordinate acquisition module, object frame creation module and object frame addition module; The layer information acquisition module is used to obtain each layer of the block and select the layer to be extracted; The object data extraction module is used to traverse the objects in the layer to be extracted; The top-level coordinate acquisition module is used to acquire the top-level boundary coordinate data of each of the objects; The object frame creation module is used to create an object frame according to the top-level boundary coordinate data of each object; The object frame adding module is used to add the object frame to the top layer of the block.

8. The system for extracting the bottom layer of a block according to claim 7, characterized in that: Also includes: Object frame merging module; The object frame merging module is used to perform overlap detection on the object frames and merge the overlapping object frames before adding the object frames to the top layer of the block.

9. An electronic device, characterized in that: The electronic device comprises a processor and a memory, wherein the memory is used to store computer program codes, and the computer program codes include computer instructions. When the processor executes the computer instructions, the electronic device executes a method for extracting the bottom layer of a block as described in any one of claims 1 to 6.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, which includes program instructions. When the program instructions are executed by a processor of an electronic device, the processor executes a method for extracting an underlying layer of a block as described in any one of claims 1 to 6.

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