Minimization of Halftone Noise in FLAT Regions for Improved Print Quality

The work in this thesis proposes a novel algorithm for enhancing the quality of flat regions in printed color image documents. The algorithm is designed to identify the flat regions based on certain criteria and filter these regions to minimize the noise prior and post Halftoning so as to make the hard copy look visibly pleasing. Noise prior to halftone process is removed using a spatial Gaussian filter together with a Hamming window, concluded from results after implementing various filtering techniques. A clustered dithering is applied in each channel of the image as Halftoning process. Furthermore, to minimize the post halftone noise, the halftone structure of the image is manipulated according to the neighboring sub-cells in their respective channels. This is done to reduce the brightness variation (a cause for noise) between the neighboring subcells. Experimental results show that the proposed algorithm efficiently minimizes noise in flat regions of mirumal gradient change in color images

FPGA BASED PARALLEL IMPLEMENTATION OF STACKED ERROR DIFFUSION ALGORITHM

Digital halftoning is a crucial technique used in digital printers to convert a continuoustone image into a pattern of black and white dots. Halftoning is used since printers have a limited availability of inks and cannot reproduce all the color intensities in a continuous image. Error Diffusion is an algorithm in halftoning that iteratively quantizes pixels in a neighborhood dependent fashion. This thesis focuses on the development and design of a parallel scalable hardware architecture for high performance implementation of a high quality Stacked Error Diffusion algorithm. The algorithm is described in ‘C’ and requires a significant processing time when implemented on a conventional CPU. Thus, a new hardware processor architecture is developed to implement the algorithm and is implemented to and tested on a Xilinx Virtex 5 FPGA chip. There is an extraordinary decrease in the run time of the algorithm when run on the newly proposed parallel architecture implemented to FPGA technology compared to execution on a single CPU. The new parallel architecture is described using the Verilog Hardware Description Language. Post-synthesis and post-implementation, performance based Hardware Description Language (HDL), simulation validation of the new parallel architecture is achieved via use of the ModelSim CAD simulation tool

MEJORA DE LA APARIENCIA VISUAL DE CÓDIGOS DE BARRAS BIDIMENSIONALES, QR-CODES, APLICANDO LA TÉCNICA DE TONOS MEDIOS

RESUMEN ANALÍTICOLos códigos de barras son imágenes binarias que contienen datos codificados. Su versión bidimensional más reciente conocida como código de rápida respuesta, QR (Quick Response) ofrece mayor ventaja respecto a otros códigos de esta clase en términos de capacidad de almacenamiento, tipos de datos a codificar y rapidez en decodificación. Recientemente, los códigos QR han recibido especial atención como alternativa publicitaria debido a que es posible decodificar la información mediante el uso de teléfonos inteligentes. Esta característica impulsó el uso de códigos QR como un medio rápido, sencillo y económico de conectar los usuarios de telefonía móvil con servicios, información y negocios en línea. Debido a su naturaleza binaria el código QR no es visualmente atractivo al usuario, ni aporta información directa sobre el tipo de contenido codificado en el mismo. Por tanto en este trabajo presenta una alternativa para mejorar la apariencia visual de los códigos QR, sin perder la calidad de la información o modificar la estructura del mismo. La propuesta consiste en técnicas de tonos medios para incrustar una imagen visualmente definida en el código QR, así como explorar las características de los algoritmos de decodificación de los mismos. El algoritmo toma ventaja del proceso de decodificación basado en la detección de la luminancia. Los valores de luminancia de la imagen a ser incrustada son modificados de acuerdo con la imagen del código QR. El resultado final de los algoritmos desarrollados es la incrustación de la imagen dentro del código QR. La distribución de pixeles a ser modificados es realizada aplicando máscaras de ruido azul. Los códigos QR generados son compatibles con lectores de códigos de barras bidimensionales estándar. Resultados experimentales muestran una mejora significativa de la apariencia visual de los códigos QR con tasas de decodificación similares a las de la versión dicromática original.PALABRAS CLAVES: Procesamiento digital de imágenes, Ruido azul, Medios tonos, Códigos QR, Librería zxing. IMPROVEMENT OF THE AESTHETIC APPEARANCE OF BIDIMENSIONAL BARCODES - (QR-CODES) BY APPLYING HALFTONE TECHNIQUESANALYTICAL SUMMARYBarcodes are binary images containing encoded data. The most recent two-dimensional version known as quick response code, QR (Quick Response) offers greater advantage than another similar codes in terms of storage capacity, data rates and faster decoding process. Recently, QR codes have received special attention as an alternative for advertising due to the possibility of decoding the information contained in the QR code, by using smartphones. This feature prompted the use of QR codes as a quick, simple and economical way to connect online mobile users with services, information and businesses. However, due to binary nature of QR code, it is not visually pleasing for users, and visual explicit information is not presented. Thus, this paper presents an alternative approach in order to improve the visual appearance of QR codes by no losing information or modifying its structure. The proposed method exploits both halftone techniques, in order to embed a visually defined image into a QR code, and also the characteristics of the decoding algorithms. This algorithm takes advantage by using the decoding process based on the luminance detection. The luminance values of image to be embedded are modified according to the QR code image. The final result of the proposed algorithm is a standard QR code, visually improved with embedded image. The distribution of pixels to be modified is performed by using blue noise masks. The generated QR codes are compatible with standard two-dimensional barcode readers. Experimental results show a significant improvement in the visual appearance of QR codes with decoding rates similar to those achieved with the original dichromatic version.KEYWORDS: Digital Image Processing, Blue noise, Halftones, QR codes, Zxing library. Forma de citar: Villarreal Dulcey, O. P., & Villamizar Mejía, R. (2014). Mejora de la apariencia visual de códigos de barras bidimensionales, QR-CODES, aplicando la técnica de tonos medios. En R, Llamosa Villalba (Ed.). Revista Gerencia Tecnológica Informática, 13(35), 33-45. ISSN 1657-8236