Hi everyone! My name is Guofu Xie, a graduate student from Graduate University of Chinese Academy of Sciences, Beijing, China. My major is Computer Graphics. This is my first year for GSoC, thank you for giving me the chance. My project is aim to implement support for HDR images in cairo. First I will implement the scRGB color space, in which each color channel has 16 bit. Second, I will extend the pixman library to support the new format of the image surface. In addition, I will use some tone mapping algorithms to represent HDR images on display media better. My proposal is below and I hope you give me some advice.Proposal Synopsis High Dynamic Range (HDR) images exceed the visualization capabilities of display and print media. It is widely used to capture a higher dynamic range of the viewed scene, from the dark shadows all the way up to bright lights or reflected highlights. Current Cairo library does not provide the HDR image surface, and the current color space can not represent the new image format. In order to effectively utilize the display capabilities, I will use scRGB color space to encode and compress the HDR image and extend the pixman library to support the new format. Deliverables The following tasks are to be developed in the project: 1) Implement the scRGB color space 2) Extend the pixman library to support the new format Project Details My efforts will actually be separate tasks to complete. First, I will implement the scRGB color space. scRGB is an RGB (Red Green Blue) color space created by Microsoft for use in its GDI+ API in Windows Vista. It uses identical color primaries and white/black points as the sRGB color space, but uses 16-bit floating point (half precision) linear values instead of gamma compressed 8-bit integers. It allows values outside of the [0..1] range, creating a much larger effective gamut. It also has greater precision because the half-precision format has a 10-bit significand. In my solution, the 16-bit floating-point data type is implemented as a C struct, half, which is designed to behave as much as possible like the standard floating-point data types built into the C language. half numbers have 1 sign bit, 5 exponent bits, and 10 mantissa bits. The interpretation of the sign, exponent and mantissa is analogous to IEEE-754 floating-point numbers. half supports normalized and denormalized numbers, infinities and NANs (Not A Number). The range of representable numbers is roughly 6.0×10-8 - 6.5×104; numbers smaller than 6.1×10-5 are denormalized. Conversions from float to half round the mantissa to 10 bits; the 13 least significant bits are lost. Conversions from half to float are lossless; all half numbers are exactly representable as float values. Second, I will add the member CAIRO_FORMAT_ARGB64 in enum variance _cairo_format_t, which is used to identify the memory format of image data. In the format, each pixel is a 64-bit quantity, with alpha in the upper 16 bits, then red, then green, then blue. The 64-bit quantities are stored native-endian. Using function cairo_image_surface_create and cairo_image_surface_create_for_data, the HDR image can be created. And then I will modify the pixman library to support the new format of image surface. In enum pixman_format_name_t, I will add the member PIXMAN_FORMAT_NAME_ARGB64, and in function pixman_format_init, I will process the PIXMAN_FORMAT_NAME_ARGB64 format. One problem with HDR has always been in viewing the images. Mundane CRTs, LCDs, prints, and other methods of displaying images only have a limited dynamic range. Thus various methods of converting HDR images into a viewable format have been developed, generally called "tone mapping". In the project, I will research on how the human eye and visual cortex perceive a scene, trying to show the whole dynamic range while retaining realistic color and contrast. In the project, I will present an adaptive logarithmic mapping approach, which was introduced in Drago et al. [2]. Of course, if there is enough time, I will implement other tone mapping algorithms, for example, Fattal et al. [3] and Mantiuk et al. [4]. Project Schedule 1) Publish my goals to the Cairo community and try to get some feedback and suggestions on my plans. I will get familiar with the specific Cairo internals that I require for my work. (Until mid of June) 2) Implement tasks in the order they are specified above. That means that I will begin with the implementation of the scRGB, the new format of image surface and HDR tone mapping algorithms. I will try to implement things so that they can be used despite they are not completely finished. (Until beginning or mid of August) 3) Testing tasks with the help of the Cairo community. This will begin as soon as one component is finished and should be completed by the end of August Biography I am a first year graduate student of Institute of Software, Chinese Academy of Sciences (ISCAS). My major is Computer Graphics. I like it and feel it very interesting and exciting. My experience in C/C++ is 5 years. Experience in graphics development and research is almost 2 years. I usually take part in Open Source activities and am vice-president of the Open Source Association of my University. In the University, my major is Software Engineering. I have led some projects, for example Chinese Chess, AutoCAD secondary development, and student management system. Now I am researching the fast Ray Tracing, GPU. I hope I can bring the new development directions for Cairo based on my current research. References [1] scRGB color space <a href="http://en.wikipedia.org/wiki/Scrgb">http://en.wikipedia.org/wiki/Scrgb</a> [2] Adaptive Logarithmic Mapping For Displaying High Contrast Scenes <a href="http://www.mpi-inf.mpg.de/resources/tmo/logmap/">http://www.mpi-inf.mpg.de/resources/tmo/logmap/</a> [3] Gradient domain high dynamic range compression <a href="http://www.cs.huji.ac.il/~danix/hdr/">http://www.cs.huji.ac.il/~danix/hdr/</a> [4] A Perceptual Framework for Contrast Processing of High Dynamic Range Images <a href="http://www.mpi-inf.mpg.de/~mantiuk/contrast_domain/">http://www.mpi-inf.mpg.de/~mantiuk/contrast_domain/</a> BEST WISHES! YOURS SINCERELY, Guofu Xie CG Group, State Key Laboratory of Computer Science, Institute of Software, Chinese Academy of Sciences(ISCAS) Tel: (+86)15810330487 Email: <a href="mailto:guofu85@gmail.com">guofu85@gmail.com</a>