Method and device for processing an image in order to construct a target image from a plurality of contiguous source images
First Claim
1. A method of processing images for constructing a digitized target image (I*) from a digitized source image (I) having a fixed frame line, and whose pixels have a digital signal value, said source and target images having a substantially common view point (P) and respective optical axes (PZ, PZ*), comprising:
- (A) calibration steps of;
determining a fixed set of orthonormal reference axes (PXa, PYa, PZa) originated at said common view point (P), defining a horizontal plane (PXa, PZa) and a vertical axis (PYa); and
storing addresses (X, Y) of points (M) situated in the source image (I), associated with respective corresponding couples of spherical coordinates (α
0, β
0), constituted of orientation angle values with respect to said set of orthonormal reference axes;
(B) initialization steps of;
storing parameters of the target image (I*), including a scale factor (d*), dimensions of the frame (2Vx *, 2Vy *), and orientation angles of the optical axis constituted by a panning angle (Θ
*) and a tilting angle (ρ
*) defined in said fixed set of orthonormal reference axes;
(C) calculation steps of;
generating an address for each pixel of the target image (I*);
generating, from said target image (I*), an image called transformed target image (H*) by using an inverse perspective transform (G-1) consisting in two successive sub-transforms;
a rotation sub-transform applied to the target image (I*) operating with a rotation angle (ρ
*) having the opposite value to the target image tilting angle (ρ
*), for generating a first vertical sub-image (R*);
a vertical translation sub-transform applied to said first vertical sub-image (R*), operating with a vertical translation vector (Y0) for generating a second vertical sub-image (H*) constituting said transformed target image (H*), having the same frame dimensions (2Vx *, 2Vy *) and the same azimuth angle as the target image (I*), and a null sight angle, and having a geometrical center (Ω
H *) situated on the optical axis (PZ*) of the target image (I*);
localizing, on the basis of the address (X*, Y*) of a pixel called initial pixel (M*) in the target image (I*), a pixel (MH *) called transformed initial pixel which corresponds to said initial pixel (M*) by said inverse perspective transform (G-1) having the same address in the transformed target image (H*), and calculating orientation angles (α
, β
) called approximate angles, with respect to said fixed set of orthonormal reference axes, of a straight line (PMH *) passing through said common view point (P) and through said transformed initial pixel (MH *);
determining an address (X, Y) of a point (M) in the source image (I), by matching, at best, said approximate orientation angles (α
, β
) with a stored spherical coordinates couple (α
0, β
0); and
calculating a function characteristic of the digital signal value (Q) at said point (M) in said source image (I) and assigning said value to said initial pixel (M*) in said target image (I*);
(D) repeating calculation steps (C) for each pixel of the target image (I*).
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Abstract
Method of processing a digital image in order to construct a calculated image, termed the target image (I*), which represents a so-called source image (I) reconstructed with modifications to the tilting angle, panning angle and scale factor in relation to this source image, including the determination of a common view point (P) for the source image (I) and the target image (I*), and of an orthonormal reference frame; the definition of an image (H*) termed the projection of the target image (I*), with geometrical center (ΩH *) aligned with the optical axis (PZ*) of the target image, with zero tilting angle, with the same panning angle (Θ*) and the same framing (2Vx*, 2Vy *) as the target image (I*) so that every pixel (M*) with address (X*, Y*) in the target image (I*) has a counterpart under projection (MH *) with the same address (X*, Y*) in the projection image (H*); the calculation by a trigonometric function (G-1), for every pixel (M*) with address (X*, Y*) in the target image, of the spherical coordinates (α, β) defining, in the reference frame, the ray linking the origin (P) to the corresponding pixel (MH *) of (H*).
68 Citations
19 Claims
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1. A method of processing images for constructing a digitized target image (I*) from a digitized source image (I) having a fixed frame line, and whose pixels have a digital signal value, said source and target images having a substantially common view point (P) and respective optical axes (PZ, PZ*), comprising:
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(A) calibration steps of; determining a fixed set of orthonormal reference axes (PXa, PYa, PZa) originated at said common view point (P), defining a horizontal plane (PXa, PZa) and a vertical axis (PYa); and storing addresses (X, Y) of points (M) situated in the source image (I), associated with respective corresponding couples of spherical coordinates (α
0, β
0), constituted of orientation angle values with respect to said set of orthonormal reference axes;(B) initialization steps of; storing parameters of the target image (I*), including a scale factor (d*), dimensions of the frame (2Vx *, 2Vy *), and orientation angles of the optical axis constituted by a panning angle (Θ
*) and a tilting angle (ρ
*) defined in said fixed set of orthonormal reference axes;(C) calculation steps of; generating an address for each pixel of the target image (I*); generating, from said target image (I*), an image called transformed target image (H*) by using an inverse perspective transform (G-1) consisting in two successive sub-transforms; a rotation sub-transform applied to the target image (I*) operating with a rotation angle (ρ
*) having the opposite value to the target image tilting angle (ρ
*), for generating a first vertical sub-image (R*);a vertical translation sub-transform applied to said first vertical sub-image (R*), operating with a vertical translation vector (Y0) for generating a second vertical sub-image (H*) constituting said transformed target image (H*), having the same frame dimensions (2Vx *, 2Vy *) and the same azimuth angle as the target image (I*), and a null sight angle, and having a geometrical center (Ω
H *) situated on the optical axis (PZ*) of the target image (I*);localizing, on the basis of the address (X*, Y*) of a pixel called initial pixel (M*) in the target image (I*), a pixel (MH *) called transformed initial pixel which corresponds to said initial pixel (M*) by said inverse perspective transform (G-1) having the same address in the transformed target image (H*), and calculating orientation angles (α
, β
) called approximate angles, with respect to said fixed set of orthonormal reference axes, of a straight line (PMH *) passing through said common view point (P) and through said transformed initial pixel (MH *);determining an address (X, Y) of a point (M) in the source image (I), by matching, at best, said approximate orientation angles (α
, β
) with a stored spherical coordinates couple (α
0, β
0); andcalculating a function characteristic of the digital signal value (Q) at said point (M) in said source image (I) and assigning said value to said initial pixel (M*) in said target image (I*); (D) repeating calculation steps (C) for each pixel of the target image (I*). - View Dependent Claims (2, 3, 4)
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5. A method of processing images for constructing a digitized target image (I*) from a number n of digitized source images (I1 . . . In) having a fixed frame line, and whose pixels have a digital signal value, said source and target images having a substantially common view point (P) and respective optical axes (PZ1 . . . PZn;
- PZ*), comprising;
(A) calibration steps of; determining a fixed set of orthonormal reference axes (PXa, PYa, PZa) originated at said common view point (P), defining a horizontal plane (PXa, PZa) and a vertical axis (PYa); and storing addresses (X, Y) of points (M) situated in the source images (I1 . . . In), associated with an index indicating a particular source image out of the n source images where a particular point (M) lies, and associated with respective corresponding couples of spherical coordinates (α
0, β
0), constituted of orientation angle values with respect to said set of orthonormal reference axes (P);(B) initialization steps of; storing parameters of the target image (I*), including a scale factor (d*), dimensions of the frame (2Vx *, 2Vy *), and orientation angles of the optical axis constituted by a panning angle (Θ
*) and a tilting angle (ρ
*) defined in said fixed set of orthonormal reference axes;(C) calculation steps of; generating an address for each pixel of the target image (I*); generating, from said target image (I*), an image called transformed target image (H*) by using an inverse perspective transform (G-1) consisting in two successive sub-transforms; a rotation sub-transform applied to the target image (I*) operating with a rotation angle (-ρ
*) having the opposite value to the target image tilting angle (ρ
*), for generating a first vertical sub-image; anda vertical translation sub-transform applied to said first vertical sub-image (R*), operating with a vertical translation vector (Y0) for generating a second vertical sub-image (H*) constituting said transformed target image (H*), having the same frame dimensions (2Vx *, 2Vy *) and the same azimuth angle as the target image (I*), and a null sight angle, and having a geometrical center (Ω
H *) situated on the optical axis of the target image (I*);localizing, on the basis of the address (X*, Y*) of a pixel called initial pixel (M*) in the target image (I*), a pixel called transformed initial pixel (MH *) which corresponds to said initial pixel (M*) by said inverse perspective transform (G-1) having the same address in the transformed target image (H*), calculating orientation angles called approximate angles (α
, β
), with respect to said fixed set of orthonormal reference axes, of a straight line (PMH *) passing through said common view point (P) and through said transformed initial pixel (MH *);determining an address (X, Y) of a point (M) and an index indicating the particular source image (Ij) where said point lies, by matching, at best, said approximate orientation angles (α
, β
) with a stored spherical coordinates couple (α
0, β
0); andcalculating a function characteristic of the digital signal value (Q) at said point (M) in said particular source image (Ij) and assigning said value to said initial pixel (M*) in said target image (I*); (D) repeating steps (C) for each pixel of the target image (I*). - View Dependent Claims (6, 7, 8, 9)
- PZ*), comprising;
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10. Am image processing device comprising:
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a system including a number n of fixed real cameras (C1 . . . Cn), n being an integer number≠
0, said cameras being arranged in such a way that their individual fields of view merge so as to form a single wide-angle field of view for observation of a panoramic scene, said real cameras providing adjacent images referred to as source images (I1 . . . In); andan image construction system simulating a mobile virtual camera (C*) continuously scanning the panoramic scene so as to form an image referred to as target image (I*) corresponding to a selected section of said wide-angle field of view, and constructed from said source images (I1 . . . In);
said systems further comprising;(A'"'"') calibration means including; means for digitizing said source and target images, in a manner that each pixel corresponds to a digital signal value; means for determining a substantially common view point (P) to said source and target images, and for determining a fixed set of orthonormal reference axes (PXa, PYa, PZa) originated at said common view point (P), defining a horizontal plane (PXa, PZa) and a vertical axis (PYa); and tabulation means for storing addresses (X, Y) of points (M) situated in the source images (I1 . . . In), associated with an index indicating a particular source image (Ij) out of the n source images (I1 . . . In) where a particular point (M) lies, and associated with respective corresponding couples of spherical coordinates (α
0, β
0), constituted of orientation angle values with respect to said set of orthonormal reference axes (P);(B'"'"') initialization means including storing means for storing parameters relating to the virtual camera (C*) for supplying parameters of the target image (I*), including a scale factor (d*), dimensions of the frame (2Vx *, 2Vy *), and orientation angles constituted by a panning angle (Θ
*) and a tilting angle (ρ
*) defined in said fixed set of orthonormal reference axes;(C'"'"') calculations means comprising an address computer including; an address generator for generating, pixel by pixel, respective addresses for the pixels of the target image (I*); an inverse perspective transform (G-1) system operating two successive sub-transforms including a rotation sub-transform and a vertical translation sub-transform for generating, from said target image (I*), an image called transformed target image (H*) having the same frame dimensions (2Vx *, 2Vy *) and the same azimuth angle as the target image (I*), and a null sight angle, and having a geometrical center (Ω
H *) situated on the optical axis of the target image (I*), said inverse perspective transform system having means for localizing, on the basis of the address (X*, Y*) of a pixel called initial pixel (M*) in the target image (I*), a pixel called transformed initial pixel (MH *) which corresponds to said initial pixel (M*) by said inverse perspective transform (G-1) having the same address in the transformed target image (H*), and said inverse perspective transform system having means for calculating orientation angles called approximate angles (α
, β
), with respect to said fixed set of orthonormal reference axes, of a straight line (PMH *) passing through said common view point (P) and through said transformed initial pixel (MH *);addressing means for determining, from the tabulation means, an address (X, Y) of a point (M) in a source image (I), and an index indicating the particular source image (Ij) where said point (M) lies, by matching, at best, the approximate orientation angles (α
, β
) related to said initial pixel (M*) with a stored spherical coordinates couple (α
0, β
0); andcalculation means for calculating a function characteristic of the digital signal value (Q) at said point (M) in said particular source image (Ij), and means for assigning said value to said initial pixel (M*) in said target image (I*). - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification