基于人眼视觉系统的JPEG压缩算法

为了提高JPEG图像压缩算法的性能,研究一种基于人眼视觉系统(HVS)模型的JPEG压缩方法。利用人眼对比度敏感函数(CSF)生成一种新的量化表,替代标准量化表应用到JPEG压缩算法的量化环节,并进行仿真实验。仿真结果表明,JPEG-HVS算法的压缩比高,解码图像质量好。与其他压缩算法相比,JPEG-HVS算法有更高的压缩比。     

不同输出设备对数字阶调再现特性的影响

为了研究不同类型输出设备对数字输出阶调再现特性的影响,选用彩色喷墨打印机Epson R250、Epson 1390、Epson 7908和Canon iPF6350,彩色激光打印机Epson C8600和Hp 4700N,热升华打印机Canon730和Sony FP97等三类输出设备对数字输出阶调再现性能进行测试和比较,得出结论:彩色喷墨打印机在图像的亮调部分再现阶调能力优于彩色激光打印机,彩色激光打印机在图像的暗调部分再现阶调能力优于彩色喷墨打印机,热升华打印机的阶调层次再现能力较好且色域相对较大。     

掌握HDR黑白

Ali Jennings告诉大家如何制作一幅包含丰富暗调、中间调、高光细节的高动态范围黑白影像一幅优秀的高动态范围（HDR）影像作品能让人们停下匆匆的脚步,驻足欣赏。使用Photoshop中的合并到HDR命令,就能实现这样的效果。我们使用多张不同曝光的照片通过数字暗房合成在一起,最终得到的照片包含从最暗到最亮的丰富细节信息,这样的高动态范围效果是通过相机拍摄完全无法实现的。     

掌握HDR黑白

<正>Ali Jennings告诉大家如何制作一幅包含丰富暗调、中间调、高光细节的高动态范围黑白影像一幅优秀的高动态范围(HDR)影像作品能让人们停下匆匆的脚步,驻足欣赏。使用Photoshop中的合并到HDR命令,就能实现这样的效果。我们使用多张不同曝光的照片通过数字暗房合成在一起,最终得到的照片包含从最暗到最亮的丰富细节信息,这样的高动态范围效果是通过相机拍摄完全无法实现的。     

液晶显示器显示性能的对比分析

显示器在图像处理领域起非常重要的作用,特别是在色彩再现及颜色调节过程中,其显色特性的好坏会直接影响到图像再现的质量。本文主要针对显示器的显示均匀性、色彩真实性及显示色域范围等性能指标进行研究,以苹果和DELL为代表,通过实验对比分析专业显示器与普通显示器的显色特性,从显示器对颜色的不同再现效果方面分析显示器性能对色彩再现效果的影响程度;从而获得影响显示器性能的3种校正参数的主次因素,为实际应用提供指导。     

不同纸张对数字输出阶调特性的影响

为了了解不同纸张对数字输出阶调特性的影响,采用CorelDraw软件制作单色色阶测试版,选择常用的普通打印纸、一般照片纸和光泽照片纸在Epson Stylus Photo R250彩色喷墨打印机上进行输出,用DS分光光度仪对输出色阶进行CIEL*a*b*色度值的测量,用色彩管理软件为不同纸张制作特性文件,对不同纸张所能达到的数字输出阶调特性进行定量分析。针对选用的纸张进行测量后得出结论,输出色彩丰富的图像优选的纸张应是光泽照片纸,输出灰度层次丰富的图像可以选择普通打印纸。     

一种基于ⅡR滤波器权值优化算法的注射机注射位置控制研究

以带输出反馈的二阶IIR滤波器作为控制研究对象,采用遗传算法作为IIR滤波器的权值优化算法,在给定区间内搜索全局最优解。针对阶跃输入信号和三角波输入信号进行注射位置控制仿真实验,验证基于权值优化算法的二阶IIR滤波器的位置控制效果。结果表明,基于遗传算法的改进IIR滤波器能够实现0超调、快速动态响应以及高控制精度,并且具有很好的动态跟踪效果。     

使用HDR获取完美曝光

标准的高动态范围图像需要合并多个不同曝光值的图像。在合并后的单张图像中，包含了所有可能的亮部和暗部细节，这种细节呈现完全超越了普通相机记录的能力。为HDR准备前期拍摄需要注意的情况主要有两个：一是确保使用三脚架来避免多次拍摄间隙可能出现的位移；另一个是对拍摄时间和空间的把握，譬如最好找空间中人相对少一些的时候，因为过多的人和相互混杂的动体会影响最终混合的效果。     

使用HDR获取完美曝光

标准的高动态范围图像需要合并多个不同曝光值的图像。在合并后的单张图像中，包含了所有可能的亮部和暗部细节，这种细节呈现完全超越了普通相机记录的能力。为HDR准备前期拍摄需要注意的情况主要有两个：一是确保使用三脚架来避免多次拍摄间隙可能出现的位移；另一个是对拍摄时间和空间的把握，譬如最好找空间中人相对少一些的时候，因为过多的人和相互混杂的动体会影响最终混合的效果。     

实时数据库数据压缩算法探讨与改进

针对历史数据压缩算法的不足,提出了一种改进的压缩算法。对历史数据的三个组成元素数值、时间标签和质量码采用不同的策略进行压缩,在数值压缩中引入了矢量数据压缩的概念。通过设立数据缓冲池,定期对数值进行一次压缩。最后对该算法进行了仿真模拟,仿真结果表明,改进算法的压缩率和压缩时间都有了显著的提高。     

Sensor interpixel correlation analysis and reduction for color filter array high dynamic range image reconstruction

High dynamic range imaging (HDRI) by bracketing of low dynamic range (LDR) images is demanding, as the sensor is deliberately operated at saturation. This exacerbates any crosstalk, interpixel capacitance, blooming and smear, all causing interpixel correlations (IC) and a deteriorated modulation transfer function (MTF). Established HDRI algorithms exclude saturated pixels, but generally overlook IC. This work presents a calibration method to estimate the affected region from saturated pixels for a color filter array (CFA) sensor, using the native CFA as a matched filter. The method minimizes color crosstalk given a set of candidates for proximity regions, and requires no special setup. Results are shown for a 21‐bit HDR output image with improved color fidelity and reduced noise. The calibration reduces IC in the LDR images and is performed only once for a given sensor. The improvement is applicable to any HDRI algorithm based on CFA image bracketing, irrespective of sensor technology. Generalizations to subsaturated and supersaturated pixels are described, facilitating a suggested irradiance‐exposure dependent point spread function charge repatriation strategy.     

Faithful representation of colours on a CRT monitor

A method is described to display faithfully on a CRT monitor the colours of images taken by a calibrated digital camera. A multicoloured “input” image, displayed on a monitor, was photographed with the camera. After correcting the digital image to take into account the gammas of both camera and monitor, the image was redisplayed as an “output” image on the same monitor. An iterative procedure found the linear matrix transformation that minimized the difference between the input and output image RGB values. We compared the efficacy of this method with two conventional methods for displaying photographed images on CRTs: the method of displaying the raw untransformed image, and the method whereby the image is transformed via the CIE common frame of reference. The results of the comparisons suggest that the iterative method produces the most faithful representation of the colours of the original image. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 388–393, 2007     

The role of colorants in the generation,storage, and output of digital still images

The purpose of this review is to highlight the important role that dye and pigment colorants play in the areas of image generation, image storage, and image output with respect to digital still images. Colorants in the form of dyes and pigments play an integral part in the digital still imaging process, from the initial conversion of the original greyscale image into a full‐colour RGB additive image, followed by electronic image storage, and finally to hard‐copy output via non‐impact printing technologies such as inkjet and thermal dye transfer. In addition, both dyes and pigments are also utilised for image generation in the fast‐developing world of electronic paper display technologies. Dyes and pigments were the mainstay of many of the early analogue photographic processes in the areas of image capture and image reproduction, and this review sets out to show that, in the new age of digital imaging, this situation is still prevalent.     

An integrated spectral imaging system for producing color images of static and moving objects

An integrated spectral imaging system constructed by synchronizing a programmable light source, a high‐speed monochrome camera, and a display device is proposed to produce tristimulus images of static and moving objects effectively in real time onto the display. This system is called the CIE‐XYZ display. Active spectral illuminants, containing both the device characteristics of camera and display, are projected onto object surfaces as time sequence. The images are captured synchronously by the camera and quickly transmitted to the display device in the RGB signal form so that the accurate tristimulus images are displayed. First, we describe the principle of the CIE‐XYZ tristimulus display. The theoretically optimal illuminants contain negative parts in the spectral curves. Second, we design practical illuminants with all positive spectral curves. The color images in our system are composed of the time sequence of RGB component images. Then, the synthesized color images on the display contain color artifacts when objects move fast. An image processing algorithm for correcting the motion color artifact is proposed based on optical flow estimation using a graphics processing unit. The comprehensive performance of the proposed system and algorithms is examined using both static and moving objects. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 329–340, 2015     

Color corrected single scale retinex based haze removal and color correction for underwater images

Underwater images are affected by scattering of dust particles leading to hazy images. The difference in absorption of light at different wavelength leads to colorcast. Restoring underwater images from haze and colorcast degradation is a challenging task. This article proposes color corrected single scale retinex algorithm for the restoration of hazy and colorcast underwater images. Further, the illumination of the underwater image is enhanced through illumination enhancer. In order to correct colorcast, the underwater images intensity shifters are proposed. Blur, natural image quality evaluator, blind/referenceless image spatial quality evaluator, entropy, peak signal to noise ratio are the metrics used to evaluate the performance of the proposed restoration technique and compared the output with the existing techniques. Compared to the existing techniques the proposed algorithm prominently removes haze and colorcast present in underwater images. The study excludes retinex-with-reset models from consideration.     

Subjective evaluation of natural high‐saturated images on a wide gamut display

In previous studies of image evaluation using wide color gamut displays, it is unclear to what degree people prefer the chroma‐varying images, especially the images that are more saturated than the most preferred image. Here, we present a study using a wide color gamut display, which measured viewers' most preferred level of image chroma (experiment 1) and their subjective evaluation of images that were less or more saturated than the previously most preferred one (experiment 2). The results showed that (a) the subjects' preferences for the original or for more saturated images depended on the images' original chroma and (b) the subjective evaluation of the images, that is, Valence and Arousal, did not deteriorate when the chroma of images increased more than the most preferred level. Such results indicate that the increase of the image chroma in wider color gamut displays can have a substantial influence on the impression images have on viewers.     

数字中间片的制作及其意义(英文)

目前数字中间片(DI)已逐渐取代电影洗印厂制作的传统中间片。在制作DI时,图像扫描成DPX文件格式。扫描仪感应的是底片的透光率,扫描所需的空间分辨率高于输出格式的空间分辨率以避免图像失真。DI有2种不同的图像编码方法;一种是用DPX文件,它表示的是底片密度,预览画面需要显示LUT;另一种方法是直接显示图像数据,在记录到胶片上之前,图像数据需要转换成密度值。记录到胶片上时,记录仪应降低M状态的红色格码值数据。如果将印片密度正确转换,则由数字中间底片印制的正片将与原底片印制的正片是相同的。本文较详细地叙述了DI的制作。     

基于角点检测的裂纹瓷图像拼接及裂纹重建

对裂纹瓷表面的纹饰进行图像拼接,可更好地应用于纹理等外部特征的分析与瓷器鉴别.图像处理技术可实现快速、无损的陶瓷器检测与分析,弥补了传统检测方法的不足.本文以具有裂纹釉的龙泉青瓷茶杯为研究对象,提取瓷器的多个侧面图像,采用Harris角点检测方法提取图像中的角点,然后进行图像配准和拼接,将多侧面图像拼接为完整图像;通过...     

数字中间片后期制作中的色彩管理

在色彩管理中使用LUT具有相当大的潜在应用价值。LUT是一个简单的数据结构,它把每一个输入值映射到相应的输出值,并且还可以确定视频硬件里每帧图像中每一个像素的数据值的大小。模仿和校正LUTs提供的转换,不但能保证多种显示器之间的匹配,而且在后期制作过程中还可以使显示的图像与胶片完美的匹配。介质中呈现的色彩组叫做色彩范围。电影正片的色彩范围与数字显示器的色彩范围具有不同的特性。数字中间片(DI)工艺有2种不同的图像编码方法:一种是使用DPX文件,其作用是进行输入和输出及表示底片密度,预览画面则需要显示LUT;另一种方法是不使用LUT而直接显示图像数据。图像数据显示的是显示器的色彩范围,而不是胶片的色彩范围。在记录到胶片上之前,数据需要转换成密度值。在制作DI过程中,可以模仿洗片厂配光工序,通过调节印片光号进行的色彩校正。本文从8个方面较详细的叙述了制作数字中间片时的色彩管理。     

热敏打印技术及热敏染料在彩色影像输出中的应用

全彩色热敏打印由于具有影像质量高、使用方便、利于环保等优点,成为彩色影像输出技术领域的发展方向。荧烷化合物具有在熔点下从无色到有色的互变结构,可通过变换取代基,得到黄、品、青系列染料,成为应用在热敏彩色影像输出技术中的主要染料类型。