imdiff.c File Reference

Image difference calculator program. More...

#include <math.h>
#include <string.h>
#include <ctype.h>
#include "imageio.h"
#include "conv.h"

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Data Structures
struct	programparams
	struct of program parameters More...
Defines
#define	DISPLAY_SCALING   255
	Display metrics for intensities in the range [0,DISPLAY_SCALING].
#define	MSSIM_K1   0.01
#define	MSSIM_K2   0.03
#define	MSSIM_C1   (MSSIM_K1*MSSIM_K1)
#define	MSSIM_C2   (MSSIM_K2*MSSIM_K2)
Enumerations
enum	metric {   DEFAULT_METRICS, MAX_METRIC, MSE_METRIC, RMSE_METRIC,   PSNR_METRIC, MSSIM_METRIC }
	enum of possible metrics More...
Functions
void	MakeDifferenceImage (float *A, const float *B, int Width, int Height, int NumChannels, float D)
	Make a difference image, Diff = (A - B)/D + 0.5.
void	BasicMetrics (float *Max, float *Mse, const float *A, const float *B, int Width, int Height, int NumChannels, int Pad)
	Compute the maximum absolute difference and the MSE.
float	ComputeMssim (const float *A, const float *B, int Width, int Height, int NumChannels, int Pad)
	Compute the Mean Structural SIMilarity (MSSIM) index.
void	PrintHelpMessage ()
	Print program usage help message.
int	main (int argc, char *argv[])

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Detailed Description

Image difference calculator program.

Author:

Pascal Getreuer <getreuer@gmail.com>

This file implements the imdiff program, a command line tool for comparing two images with various image quality metrics. The possible metrics are

• Maximum absolute difference, max_n |A_n - B_n|
• Mean squared error, 1/N sum |A_n - B_n|^2
• Root mean squared error, (MSE)^1/2
• Peak signal-to-noise ratio, -10 log10(MSE/255^2)
• Mean structural similarity index (MSSIM) where N is the number of pixels and subscript n denotes the nth pixel.

The program can also create a difference image, computed as D_n = 255/20 (A_n - B_n) + 255/2 where values outside of the range [0,255] are saturated.

Image alpha channels are ignored. Also beware that although the program can read 16-bit PNG images (provided LIBPNG_SUPPORT is enabled), the image data is quantized internally to 8 bits.

Copyright (c) 2010-2011, Pascal Getreuer All rights reserved.

This program is free software: you can use, modify and/or redistribute it under the terms of the simplified BSD License. You should have received a copy of this license along this program. If not, see <http://www.opensource.org/licenses/bsd-license.html>.

Definition in file imdiff.c.

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Define Documentation

#define DISPLAY_SCALING   255

Display metrics for intensities in the range [0,DISPLAY_SCALING].

Definition at line 42 of file imdiff.c.

#define MSSIM_C1   (MSSIM_K1*MSSIM_K1)

Definition at line 47 of file imdiff.c.

#define MSSIM_C2   (MSSIM_K2*MSSIM_K2)

Definition at line 48 of file imdiff.c.

#define MSSIM_K1   0.01

Definition at line 44 of file imdiff.c.

#define MSSIM_K2   0.03

Definition at line 45 of file imdiff.c.

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Enumeration Type Documentation

enum metric

enum of possible metrics

Enumerator:

DEFAULT_METRICS
MAX_METRIC
MSE_METRIC
RMSE_METRIC
PSNR_METRIC
MSSIM_METRIC

Definition at line 52 of file imdiff.c.

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Function Documentation

void BasicMetrics	(	float *	Max,
		float *	Mse,
		const float *	A,
		const float *	B,
		int	Width,
		int	Height,
		int	NumChannels,
		int	Pad
	)

Compute the maximum absolute difference and the MSE.

Definition at line 292 of file imdiff.c.

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float ComputeMssim	(	const float *	A,
		const float *	B,
		int	Width,
		int	Height,
		int	NumChannels,
		int	Pad
	)

Compute the Mean Structural SIMilarity (MSSIM) index.

Definition at line 319 of file imdiff.c.

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int main	(	int	argc,
		char *	argv[]
	)

Definition at line 120 of file imdiff.c.

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void MakeDifferenceImage	(	float *	A,
		const float *	B,
		int	Width,
		int	Height,
		int	NumChannels,
		float	D
	)

Make a difference image, Diff = (A - B)/D + 0.5.

Definition at line 278 of file imdiff.c.

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void PrintHelpMessage

(

)

Print program usage help message.

Definition at line 88 of file imdiff.c.