Resolution Conversion (Resize)

Resolution Conversion is the method used to resize the source image to the size of the destination image. Different types of interpolation techniques can be used in resize function, namely: Nearest-neighbor, Bilinear, and Area interpolation. The type of interpolation can be passed as a template parameter to the API. The following enumeration types can be used to specify the interpolation type:

XF_INTERPOLATION_NN - For Nearest-neighbor interpolation
XF_INTERPOLATION_BILINEAR - For Bilinear interpolation
XF_INTERPOLATION_AREA - For Area interpolation

Note: Scaling factors greater than or equal to 0.25 are supported in down-scaling and values less than or equal to 8 are supported for up-scaling.

API Syntax

template<int INTERPOLATION_TYPE, int TYPE, int SRC_ROWS, int SRC_COLS, int DST_ROWS, int DST_COLS, int NPC, int MAX_DOWN_SCALE, int XFCVDEPTH_IN = _XFCVDEPTH_DEFAULT, int XFCVDEPTH_OUT = _XFCVDEPTH_DEFAULT>
void resize (xf::cv::Mat<TYPE, SRC_ROWS, SRC_COLS, NPC, XFCVDEPTH_IN> & _src, xf::cv::Mat<TYPE, DST_ROWS, DST_COLS, NPC, XFCVDEPTH_OUT> & _dst)

Parameter Descriptions

The following table describes the template and the function parameters.

Table 688 Table . resize Parameter Description
Parameter	Description
INTERPOLATIO N_TYPE	Interpolation type. The different options possible are XF_INTERPOLATION_NN – Nearest Neighbor Interpolation XF_INTERPOLATION_BILINEAR – Bilinear interpolation XF_INTERPOLATION_AREA – Area Interpolation
TYPE	Input and Output pixel type. Only 8-bit, unsigned, 1 and 3 channels are supported (XF_8UC1 and XF_8UC3)
SRC_ROWS	Maximum Height of input image for which the hardware kernel would be built.
SRC_COLS	Maximum Width of input image for which the hardware kernel would be built (must be a multiple of 8).
DST_ROWS	Maximum Height of output image for which the hardware kernel would be built.
DST_COLS	Maximum Width of output image for which the hardware kernel would be built (must be a multiple of 8).
NPC	Number of pixels to be processed per cycle. Possible options are XF_NPPC1 (1 pixel per cycle) and XF_NPPC8 (8 pixel per cycle).
MAX_DOWN_SCA LE	Set to 2 for all 1 pixel modes, and for upscale in x direction. When down scaling in x direction in 8-pixel mode, please set this parameter to the next highest integer value of the down scale factor i.e., if downscaling from 1920 columns to 1280 columns, set to 2. For 1920 to 640, set to 3.
XFCVDEPTH_IN	Depth of the input image.
XFCVDEPTH_OUT	Depth of the output image.
_src	Input Image
_dst	Output Image

Resource Utilization

The following table summarizes the resource utilization of Resize function in Resource Optimized (8 pixel) mode and Normal mode, as generated in the Vivado HLS 2019.1 tool for the Xilinx xczu9eg-ffvb1156-2-i-es2 FPGA.

Table 689 Table . resize Function Resource Utilization Summary
Operating Mode	Utilization Estimate
	1 Pixel (at 300 MHz)					8 Pixel (at 150MHz)
	IMAGESIZE	LUTs	FFs	DSPs	BRAMs	IMAGESIZE	LUTs	FFs	DSPs	BRAMs
Downscale Nearest Neighbor	1920X1080 TO 960X1620	1089	1593	4	2	3840X2160 TO 1920X1080	2545	2250	4	12
Downscale Bilinear	1920X1080 TO 960X1080	1340	1846	8	2	3840X2160 TO 1920X1080	5159	3092	36	12
Downscale Area	3840X2160 TO 1920X1080	6146	8338	19	10	3840X2160 TO 1920X1080	17892	19758	162	16
Upscale Nearest Neighbor	1920X1080 TO 3840X540	1089	1593	4	2	1920X1080 TO 3840X2160	1818	1686	4	6
Upscale Bilinear	1920X1080 TO 3840X540	1340	1846	8	2	1920X1080 TO 3840X2160	3697	2739	36	6
Upscale Area	1920X1080 TO 3840X2160	5811	8773	28	32	1920X1080 TO 3840X2160	12214	14003	98	24

The following table summarizes the resource utilization of Resize function in Normal mode, as generated in the Vivado HLS 2019.1 tool for the Xilinx xczu9eg-ffvb1156-2-i-es2 FPGA for 3channel image as input.

Table 690 Table . resize Function Resource Utilization Summary
Operating Mode	Utilization Estimate
	1 Pixel (at 300 MHz)
	IMAGESIZE	LUTs	FFs	DSPs	BRAMs
Downscale Nearest Neighbor	3840X2160 TO 1920X108	1184	168	4	18
Downscale Bilinear	3840X2160 TO 1920X1080	1592	2058	14	18
Downscale Area	3840X2160 TO 1920X1080	3212	4777	104	72
Upscale Nearest Neighbor	1920X1080 TO 3840X2160	1166	1697	4	9
Upscale Bilinear	1920X1080 TO 3840X2160	1574	2053	14	9
Upscale Area	1920X1080 TO 3840X2160	1731	2733	36	31

Performance Estimate

The following table summarizes the performance estimation of Resize for various configurations, as generated in the Vivado HLS 2019.1 tool for the xczu9eg-ffvb1156-2-i-es2 FPGA at 300 MHz to resize a grayscale image from 1080x1920 to 480x640 (downscale); and to resize a grayscale image from 1080x1920 to 2160x3840 (upscale). This table also shows the latencies obtained for different interpolation types.

Table 691 Table . resize Function Performance Estimate Summary
Operating Mode	Operating Frequency (MHz)	Latency Estimate (ms)
Operating Mode	Operating Frequency (MHz)	Downscale NN	Downscale Bilinear	Downscale Area	Upscale NN	Upscale Bilinear	Upscale Area
1 pixel	300	6.94	6.97	7.09	27.71	27.75	27.74

Resolution Conversion (Resize) - 2023.1 English

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