Stochastic Modeling and Resolution-Free Rendering of Film Grain

The realistic synthesis and rendering of film grain is a crucial goal for many amateur and professional photographers and film-makers whose artistic works require the authentic feel of analog photography. The objective of this work is to propose an algorithm that reproduces the visual aspect of film grain texture on any digital image. Previous approaches to this problem either propose unrealistic models or simply blend scanned images of film grain with the digital image, in which case the result is inevitably limited by the quality and resolution of the initial scan. In this work, we introduce a stochastic model to approximate the physical reality of film grain, and propose a resolution-free rendering algorithm to simulate realistic film grain for any digital input image. By varying the parameters of this model, we can achieve a wide range of grain types. We demonstrate this by comparing our results with film grain examples from dedicated software, and show that our rendering results closely resemble these real film emulsions. In addition to realistic grain rendering, our resolution-free algorithm allows for any desired zoom factor, even down to the scale of the microscopic grains themselves

Rendering Deformed Speckle Images with a Boolean Model

International audienceRendering speckle images affected by a given deformation field is of primary importance to assess the metrological performance of displacement measurement methods used in experimental mechanics and based on digital image correlation (DIC). This article describes how to render deformed speckle images with a classic model of stochastic geometry, the Boolean model. The advantage of the proposed approach is that it does not depend on any interpolation scheme likely to bias the assessment process, and that it allows the user to render speckle images deformed with any deformation field given by an analytic formula. The proposed algorithm mimics the imaging chain of a digital camera, and its parameters are carefully discussed. A MATLAB software implementation and synthetic ground-truth datasets for assessing DIC software programs are publicly available

Realistic Film Grain Rendering

International audienceFilm grain is the unique texture which results from the silver halide based analog photographic process. Film emulsions are made up of microscopic photo-sensitive silver grains, and the fluctuating density of these grains leads to what is known as film grain. This texture is valued by photographers and film directors for its artistic value. We present two implementations of a film grain rendering algorithm based on a physically realistic film grain model. The rendering algorithm uses a Monte Carlo simulation to determine the value of each output rendered pixel. A significant advantage of using this model is that the images can be rendered at any resolution, so that arbitrary zoom factors are possible, even to the point where the individual grains can be observed. We provide a method to choose the best implementation automatically, with respect to execution time. The C++ code for this work is available, as well as an online demo http://dev.ipol.im/~nfaraj/ipol_demo/film_grain/