Output Images

Computation Time

General Evaluation

It is a process of compressing or scaling down the dynamic range of generated WDR image so that it can be displayed properly on LDR display device.

Range of luminance (or illuminance) measured in cd/m2 [8](Source: CambridgeInColor.com)

During image capture, dynamic range of original scene is reduced due to limited capability of camera sensor to map all scene’s intensity levels. The reduction from wide dynamic range to low dynamic range will cause some losses of image details.

Reduction of dynamic range of original scene during image capture(Source: CambridgeInColor.com)

Image GenerationTo solve the previous problem, one has to generate a WDR image which covers almost all scene’s intensity levels. Therefore, losses of image details can be minimized.

Image VisualizationThe generated WDR image will then have wider dynamic range. However, the conventional LDR display devices like CRT and LCD have low dynamic range. Therefore, not all intensity levels of WDR image can be displayed. To solve this problem, dynamic range of WDR image must be scaled down so that it can be displayed properly on LDR display.

NAME : WAZIRAH BINTI MD ESAID NUMBER : 8998SUPERVISOR : DR. AAMIR SAEED MALIK

SLOT NUMBER : 66

IMPLEMENTATION AND ANALYSISOF

WIDE DYNAMIC RANGE IMAGING METHODS

Dynamic range of original scene

Dynamic range of captured image

Problem Statement

Background

WDR Image Generation

WDR Image Visualization (Tone-Mapping)

Objectives and Project Scopes

Methodology

Results and Discussion

The computation time is affected by the algorithm complexity and the size of input images used.

Most people prefer output images with good visibility and color appearance.

Dynamic RangeIt is a ratio of the maximum measurable intensity to the minimum detectable intensity level in scenes, images and display devices.

Wide Dynamic Range (WDR) ImagingIt is a solution for improving low dynamic range (LDR) images captured from scenes which have both bright and dark areas. It is acquired especially when scenes of interest have wide range of light intensity variations.

To implement methods of WDR image generation To implement methods of WDR visualization or tone-mapping To analyze the output images resulted from the implemented WDR tone-mapping

methods through both objective and subjective measures

Conclusion

It is a process of generating an image with wider dynamic range by combining LDR images with different exposure settings to cover almost all scene’s intensity levels.

WDR Image

WDR Image

Method Selection

LDR Images

WDR Image Generation

WDR Image Visualization(Tone-Mapping)

Analysis

WDR Image

LDR Image

SubjectiveGeneral Evaluation

ObjectiveComputation Time

A: Logarithmic B: Logarithmic (Modified)

C: Exponential(δ = 0.0001)

D: Exponential(δ = 0.001)

E: Exponential(δ = 0.01)

F: Exponential(δ = 0.1)

G: Exponential(Modified, δ = 0.0001)

H: Exponential(Modified, δ = 0.001)

I: Exponential(Modified, δ = 0.01)

J: Exponential(Modified, δ = 0.1)

K: Reinhard et al (Global Operator)

L: Reinhard et al (Local Operator)

M: Garrett et al N: MATLAB O: Photomatix (Details Enhancer)

P: Photomatix (Tone Compressor)

Rank Algorithm Overall Average Rating1 Reinhard et al (Local Operator) 2.416672 Reinhard et al (Global Operator) 2.488103 Photomatix (Tone Compressor) 2.654764 Exponential (δ = 0.01) 2.845245 Photomatix (Details Enhancer) 2.952386 Exponential (δ = 0.001) 3.023817 Exponential (δ = 0.0001) 3.059528 Exponential (δ = 0.1) 3.107149 Garrett et al 3.38333

10 MATLAB (tonemap) 3.4166711 Exponential (Modified, δ = 0.1) 4.0357112 Exponential (Modified, δ = 0.01) 4.1428613 Logarithmic 4.6309514 Exponential (Modified, δ = 0.001) 4.6904815 Exponential (Modified, δ = 0.0001) 4.8095216 Logarithmic (Modified) 5.17857

12 persons have evaluated all output images. Rating scale is set between 1 (best) and 6 (worst).

The fastest: Logarithmic, Exponential and Reinhard et al (Global Operator)

The slowest: Reinhard et al (Local Operator)

Implemented AlgorithmsWDR Image Generation: MATLAB function (“makehdr”)

WDR Image Visualization (Tone-Mapping): Logarithmic, Exponential, Reinhard et al (Global Operator), Reinhard et al (Local Operator), and Garrett et al. Also, MATLAB function (“tonemap”) and Photomatix (Details Enhancer and Tone Compressor) for comparison purpose.

Ranked algorithms according to their overall average rating.