Functions | |
| static __INLINE float32_t | arm_bilinear_interp_f32 (const arm_bilinear_interp_instance_f32 *S, float32_t X, float32_t Y) |
| static __INLINE q31_t | arm_bilinear_interp_q31 (arm_bilinear_interp_instance_q31 *S, q31_t X, q31_t Y) |
| static __INLINE q15_t | arm_bilinear_interp_q15 (arm_bilinear_interp_instance_q15 *S, q31_t X, q31_t Y) |
| static __INLINE q7_t | arm_bilinear_interp_q7 (arm_bilinear_interp_instance_q7 *S, q31_t X, q31_t Y) |
Bilinear interpolation is an extension of linear interpolation applied to a two dimensional grid. The underlying function f(x, y) is sampled on a regular grid and the interpolation process determines values between the grid points. Bilinear interpolation is equivalent to two step linear interpolation, first in the x-dimension and then in the y-dimension. Bilinear interpolation is often used in image processing to rescale images. The CMSIS DSP library provides bilinear interpolation functions for Q7, Q15, Q31, and floating-point data types.
Algorithm
typedef struct
{
uint16_t numRows;
uint16_t numCols;
float32_t *pData;
} arm_bilinear_interp_instance_f32;
numRows specifies the number of rows in the table; numCols specifies the number of columns in the table; and pData points to an array of size numRows*numCols values. The data table pTable is organized in row order and the supplied data values fall on integer indexes. That is, table element (x,y) is located at pTable[x + y*numCols] where x and y are integers.(x, y) specify the desired interpolation point. Then define:
XF = floor(x)
YF = floor(y)
f(x, y) = f(XF, YF) * (1-(x-XF)) * (1-(y-YF))
+ f(XF+1, YF) * (x-XF)*(1-(y-YF))
+ f(XF, YF+1) * (1-(x-XF))*(y-YF)
+ f(XF+1, YF+1) * (x-XF)*(y-YF)
Note that the coordinates (x, y) contain integer and fractional components. The integer components specify which portion of the table to use while the fractional components control the interpolation processor.| static __INLINE float32_t arm_bilinear_interp_f32 | ( | const arm_bilinear_interp_instance_f32 * | S, |
| float32_t | X, | ||
| float32_t | Y | ||
| ) | [static] |
Floating-point bilinear interpolation.
| [in,out] | *S | points to an instance of the interpolation structure. |
| [in] | X | interpolation coordinate. |
| [in] | Y | interpolation coordinate. |
Definition at line 6739 of file arm_math.h.
| static __INLINE q31_t arm_bilinear_interp_q31 | ( | arm_bilinear_interp_instance_q31 * | S, |
| q31_t | X, | ||
| q31_t | Y | ||
| ) | [static] |
Q31 bilinear interpolation.
| [in,out] | *S | points to an instance of the interpolation structure. |
| [in] | X | interpolation coordinate in 12.20 format. |
| [in] | Y | interpolation coordinate in 12.20 format. |
Definition at line 6806 of file arm_math.h.
| static __INLINE q15_t arm_bilinear_interp_q15 | ( | arm_bilinear_interp_instance_q15 * | S, |
| q31_t | X, | ||
| q31_t | Y | ||
| ) | [static] |
Q15 bilinear interpolation.
| [in,out] | *S | points to an instance of the interpolation structure. |
| [in] | X | interpolation coordinate in 12.20 format. |
| [in] | Y | interpolation coordinate in 12.20 format. |
Definition at line 6882 of file arm_math.h.
| static __INLINE q7_t arm_bilinear_interp_q7 | ( | arm_bilinear_interp_instance_q7 * | S, |
| q31_t | X, | ||
| q31_t | Y | ||
| ) | [static] |
Q7 bilinear interpolation.
| [in,out] | *S | points to an instance of the interpolation structure. |
| [in] | X | interpolation coordinate in 12.20 format. |
| [in] | Y | interpolation coordinate in 12.20 format. |
Definition at line 6962 of file arm_math.h.
1.7.2