Super-resolution benchmarking {#tutorial_dnn_superres_benchmark}
===========================
Benchmarking
----
The super-resolution module contains sample codes for benchmarking, in order to compare different models and algorithms.
Here is presented a sample code for performing benchmarking, and then a few benchmarking results are collected.
It was performed on an Intel i7-9700K CPU on an Ubuntu 18.04.02 OS.
Source Code of the sample
-----------
@includelineno dnn_superres/samples/dnn_superres_benchmark_quality.cpp
Explanation
-----------
-# **Read and downscale the image**
@code{.cpp}
int width = img.cols - (img.cols % scale);
int height = img.rows - (img.rows % scale);
Mat cropped = img(Rect(0, 0, width, height));
Mat img_downscaled;
cv::resize(cropped, img_downscaled, cv::Size(), 1.0 / scale, 1.0 / scale);
@endcode
Resize the image by the scaling factor. Before that a cropping is necessary, so the images will align.
-# **Set the model**
@code{.cpp}
DnnSuperResImpl sr;
sr.readModel(path);
sr.setModel(algorithm, scale);
sr.upsample(img_downscaled, img_new);
@endcode
Instantiate a dnn super-resolution object. Read and set the algorithm and scaling factor.
-# **Perform benchmarking**
@code{.cpp}
double psnr = PSNR(img_new, cropped);
Scalar q = cv::quality::QualitySSIM::compute(img_new, cropped, cv::noArray());
double ssim = mean(cv::Vec3f(q[0], q[1], q[2]))[0];
@endcode
Calculate PSNR and SSIM. Use OpenCVs PSNR (core opencv) and SSIM (contrib) functions to compare the images.
Repeat it with other upscaling algorithms, such as other DL models or interpolation methods (eg. bicubic, nearest neighbor).
Benchmarking results
-----------
Dataset benchmarking
----
###General100 dataset
#####2x scaling factor
| | Avg inference time in sec (CPU)| Avg PSNR | Avg SSIM |
| ------------- |:-------------------:| ---------:|--------:|
| ESPCN | **0.008795** | 32.7059 | 0.9276 |
| EDSR | 5.923450 | **34.1300** | **0.9447** |
| FSRCNN | 0.021741 | 32.8886 | 0.9301 |
| LapSRN | 0.114812 | 32.2681 | 0.9248 |
| Bicubic | 0.000208 | 32.1638 | 0.9305 |
| Nearest neighbor | 0.000114 | 29.1665 | 0.9049 |
| Lanczos | 0.001094 | 32.4687 | 0.9327 |
#####3x scaling factor
| | Avg inference time in sec (CPU)| Avg PSNR | Avg SSIM |
| ------------- |:-------------------:| ---------:|--------:|
| ESPCN | **0.005495** | 28.4229 | 0.8474 |
| EDSR | 2.455510 | **29.9828** | **0.8801** |
| FSRCNN | 0.008807 | 28.3068 | 0.8429 |
| LapSRN | 0.282575 |26.7330 |0.8862 |
| Bicubic | 0.000311 |26.0635 |0.8754 |
| Nearest neighbor | 0.000148 |23.5628 |0.8174 |
| Lanczos | 0.001012 |25.9115 |0.8706 |
#####4x scaling factor
| | Avg inference time in sec (CPU)| Avg PSNR | Avg SSIM |
| ------------- |:-------------------:| ---------:|--------:|
| ESPCN | **0.004311** | 26.6870 | 0.7891 |
| EDSR | 1.607570 | **28.1552** | **0.8317** |
| FSRCNN | 0.005302 | 26.6088 | 0.7863 |
| LapSRN | 0.121229 |26.7383 |0.7896 |
| Bicubic | 0.000311 |26.0635 |0.8754 |
| Nearest neighbor | 0.000148 |23.5628 |0.8174 |
| Lanczos | 0.001012 |25.9115 |0.8706 |
Images
----
####2x scaling factor
|Set5: butterfly.png | size: 256x256 | ||
|:-------------:|:-------------------:|:-------------:|:----:|
|||| |
|PSRN / SSIM / Speed (CPU)|26.6645 / 0.9048 / 0.000201 |23.6854 / 0.8698 / **0.000075** | **26.9476** / **0.9075** / 0.001039|
|  |  | 
|29.0341 / 0.9354 / **0.004157**| 29.0077 / 0.9345 / 0.006325 | 27.8212 / 0.9230 / 0.037937 | **30.0347** / **0.9453** / 2.077280 |
####3x scaling factor
|Urban100: img_001.png | size: 1024x644 | ||
|:-------------:|:-------------------:|:-------------:|:----:|
|||| |
|PSRN / SSIM / Speed (CPU)| 27.0474 / **0.8484** / 0.000391 | 26.0842 / 0.8353 / **0.000236** | **27.0704** / 0.8483 / 0.002234|
||  | LapSRN is not trained for 3x
because of its architecture | 
|28.0118 / 0.8588 / **0.030748**| 28.0184 / 0.8597 / 0.094173 | | **30.5671** / **0.9019** / 9.517580 |
####4x scaling factor
|Set14: comic.png | size: 250x361 | ||
|:-------------:|:-------------------:|:-------------:|:----:|
|||| |
|PSRN / SSIM / Speed (CPU)| **19.6766** / **0.6413** / 0.000262 |18.5106 / 0.5879 / **0.000085** | 19.4948 / 0.6317 / 0.001098|
||  |  | 
|20.0417 / 0.6302 / **0.001894**| 20.0885 / 0.6384 / 0.002103 | 20.0676 / 0.6339 / 0.061640 | **20.5233** / **0.6901** / 0.665876 |
####8x scaling factor
|Div2K: 0006.png | size: 1356x2040 | |
|:-------------:|:-------------------:|:-------------:|
||||
|PSRN / SSIM / Speed (CPU)| 26.3139 / **0.8033** / 0.001107| 23.8291 / 0.7340 / **0.000611** |
||  | |
|26.1565 / 0.7962 / 0.004782| **26.7046** / 0.7987 / 2.274290 | |