Dwayne Phillips' "Image Processing in C" offers a practical, code-driven introduction to image manipulation techniques. The book focuses on foundational concepts and algorithms, providing C code examples for tasks like reading and writing various image formats, performing histogram equalization, implementing spatial filtering (smoothing and sharpening), edge detection, and dithering. It prioritizes clarity and simplicity over complex mathematical derivations, making it accessible to programmers seeking a hands-on approach to learning image processing basics. While the book uses older image formats and C libraries, the core principles and algorithms remain relevant for understanding fundamental image processing operations.
"The Night Watch" argues that modern operating systems are overly complex and difficult to secure due to the accretion of features and legacy code. It proposes a "clean-slate" approach, advocating for simpler, more formally verifiable microkernels. This would entail moving much of the OS functionality into user space, enabling better isolation and fault containment. While acknowledging the challenges of such a radical shift, including performance concerns and the enormous effort required to rebuild the software ecosystem, the paper contends that the long-term benefits of improved security and reliability outweigh the costs. It emphasizes that the current trajectory of increasingly complex OSes is unsustainable and that a fundamental rethinking of system design is crucial to address the growing security threats facing modern computing.
HN users discuss James Mickens' humorous USENIX keynote, "The Night Watch," focusing on its entertaining delivery and insightful points about the complexities and frustrations of systems work. Several commenters praise Mickens' unique presentation style and the relatable nature of his anecdotes about debugging, legacy code, and the challenges of managing distributed systems. Some highlight specific memorable quotes and jokes, appreciating the blend of humor and technical depth. Others reflect on the timeless nature of the talk, noting how the issues discussed remain relevant years later. A few commenters express interest in seeing a video recording of the presentation.
Driven by a desire for simplicity and performance in a personal project involving embedded systems and game development, the author rediscovered their passion for C. After years of working with higher-level languages, they found the direct control and predictable behavior of C refreshing and efficient. This shift allowed them to focus on core programming principles and optimize their code for resource-constrained environments, ultimately leading to a more satisfying and performant outcome than they felt was achievable with more complex tools. They argue that while modern languages offer conveniences, C's close-to-the-metal nature provides a unique learning experience and performance advantage, particularly for certain applications.
HN commenters largely agree with the author's points about C's advantages, particularly its predictability and control over performance. Several praised the feeling of being "close to the metal" and the satisfaction of understanding exactly how the code interacts with the hardware. Some offered additional benefits of C, such as easier debugging due to its simpler execution model and its usefulness in constrained environments. A few commenters cautioned against romanticizing C, pointing out its drawbacks like manual memory management and the potential for security vulnerabilities. One commenter suggested Zig as a modern alternative that addresses some of C's shortcomings while maintaining its performance benefits. The discussion also touched on the enduring relevance of C, particularly in foundational systems and performance-critical applications.
This blog post presents a revised and more robust method for invoking raw OpenBSD system calls directly from C code, bypassing the standard C library. It improves upon a previous example by handling variable-length argument lists and demonstrating how to package those arguments correctly for system calls. The core improvement involves using assembly code to dynamically construct the system call arguments on the stack and then execute the syscall instruction. This allows for a more general and flexible approach compared to hardcoding argument handling for each specific system call. The provided code example demonstrates this technique with the getpid() system call.
Several Hacker News commenters discuss the impracticality of the raw syscall demo, questioning its real-world usefulness and emphasizing that libraries like libc exist for a reason. Some appreciated the technical depth and the exploration of low-level system interaction, viewing it as an interesting educational exercise. One commenter suggested the demo could be useful for specialized scenarios like writing a dynamic linker or a microkernel. There was also a brief discussion about the performance implications and the idea that bypassing libc wouldn't necessarily result in significant speed improvements, and might even be slower in some cases. Some users also debated the portability of the code and suggested alternative methods for achieving similar results.
The blog post explores how C, despite lacking built-in object-oriented features like polymorphism, achieves similar functionality through clever struct design and function pointers. It uses examples from the Linux kernel and FFmpeg to demonstrate this. Specifically, it showcases how defining structs with common initial members (akin to base classes) and using function pointers within these structs allows different "derived" structs to implement their own versions of specific operations, effectively mimicking virtual methods. This enables flexible and extensible code that can handle various data types or operations without needing to know the specific concrete type at compile time, achieving runtime polymorphism.
Hacker News users generally praised the article for its clear explanation of polymorphism in C, particularly how FFmpeg and the Linux kernel utilize function pointers and structs to achieve object-oriented-like designs. Several commenters pointed out the trade-offs of this approach, highlighting the increased complexity for debugging and the potential performance overhead compared to simpler C code or using C++. One commenter shared personal experience working with FFmpeg's codebase, confirming the article's description of its design. Another noted the value in understanding these techniques even if using higher-level languages, as it helps with interacting with C libraries and understanding lower-level system design. Some discussion focused on the benefits and drawbacks of C++'s object model compared to C's approach, with some suggesting modern C++ offers a more manageable way to achieve polymorphism. A few commenters mentioned other examples of similar techniques in different C projects, broadening the context of the article.
The F8 is a new 8-bit computer architecture designed for efficiency in both code size and memory usage, especially when programming in C. It aims to achieve performance comparable to 16-bit systems while maintaining the simplicity and resource efficiency of 8-bit designs. This is accomplished through features like a hybrid stack/register-based architecture, variable-width instructions, and dedicated instructions for common C operations like pointer manipulation and function calls. The F8 also emphasizes practical applications with features like a built-in bootloader and support for direct connection to peripherals.
Hacker News users discussed the F8 architecture's unusual design choices. Several commenters questioned the practical applications given the performance tradeoffs for memory efficiency, particularly with modern memory availability. Some debated the value of 8-bit architectures in niche applications like microcontrollers, while others pointed out existing alternatives like AVR. The unusual register structure and lack of hardware stack were also discussed, with some suggesting it might hinder C compiler optimization. A few expressed interest in the unique approach, though skepticism about real-world viability was prevalent. Overall, the comments reflected a cautious curiosity towards F8 but with reservations about its usefulness compared to established architectures.
The blog post showcases efficient implementations of hash tables and dynamic arrays in C, prioritizing speed and simplicity over features. The hash table uses open addressing with linear probing and a power-of-two size, offering fast lookups and insertions. Resizing is handled by allocating a larger table and rehashing all elements, a process triggered when the table reaches a certain load factor. The dynamic array, built atop realloc, doubles in capacity when full, ensuring amortized constant-time appends while minimizing wasted space. Both examples emphasize practical performance over complex optimizations, providing clear and concise code suitable for embedding in performance-sensitive applications.
Hacker News users discuss the practicality and efficiency of Chris Wellons' C implementations of hash tables and dynamic arrays. Several commenters praise the clear and concise code, finding it a valuable learning resource. Some debate the choice of open addressing over separate chaining for the hash table, with proponents of open addressing citing better cache locality and less memory overhead. Others highlight the importance of proper hash functions and the potential performance degradation with high load factors in open addressing. A few users suggest alternative approaches, such as using C++ containers or optimizing for specific use cases, while acknowledging the educational value of Wellons' straightforward C examples. The discussion also touches on the trade-offs of manual memory management and the challenges of achieving both simplicity and performance.
This project introduces a C-based web framework designed for dynamic module loading and hot reloading. Leveraging a custom module format and a simple HTTP server, it allows developers to modify and reload C code without restarting the server, facilitating rapid development and experimentation. The framework compiles and links modules on-the-fly, managing dependencies and updating the running server seamlessly. While currently limited in features, it aims to offer a performant and flexible foundation for building web applications directly in C.
Hacker News users discussed the practicality and novelty of a C web framework with hot reloading. Some questioned the real-world use cases and performance benefits compared to existing solutions, suggesting the project serves more as an interesting experiment than a production-ready tool. Others expressed interest in the technical implementation, particularly the hot reloading aspect, and appreciated the author's effort in exploring this concept. Several users pointed out potential issues like memory leaks and the challenges of safely reloading C code in a web server environment. The overall sentiment leans towards acknowledging the project's technical ingenuity while remaining skeptical about its broad applicability.
Summary of Comments ( 16 )
https://news.ycombinator.com/item?id=43359343
Hacker News users discussing Dwayne Phillips' "Image Processing in C" generally praise its clarity and practicality, especially for beginners. Several commenters highlight its focus on fundamental concepts and algorithms, making it a good foundational resource even if the C code itself is dated. Some suggest pairing it with more modern libraries like OpenCV for practical application. A few users point out its limitations, such as the lack of coverage on more advanced topics, while others appreciate its conciseness and accessibility compared to denser academic texts. The code examples are praised for their simplicity and illustrative nature, promoting understanding over optimized performance.
The Hacker News post titled "Image Processing in C – Dwayne Phillips [pdf]" (https://news.ycombinator.com/item?id=43359343) has a modest number of comments, sparking a discussion around the linked PDF book on image processing in C.
One commenter reminisces about using similar techniques in the 1990s for image processing on embedded systems, highlighting the historical context of the book's approach. They also point out that while the methods described might seem basic now, they were cutting-edge at the time and provided a valuable foundation for understanding fundamental image manipulation principles. This commenter emphasizes the importance of appreciating the evolution of the field and recognizing the significance of these older techniques.
Another commenter discusses the practical aspects of working with image data in C, specifically mentioning the importance of understanding memory layout and pointer arithmetic for efficient manipulation of pixel data. They underscore the educational value of the book in teaching these low-level concepts, which are often abstracted away in modern libraries and frameworks. This commenter also highlights the importance of such low-level understanding for optimizing performance in resource-constrained environments.
A further comment draws attention to the challenges of cross-platform compatibility when working with raw image data in C. They note the prevalence of different byte orders and color formats, emphasizing the need for careful handling of these variations to ensure correct image display and processing across different systems.
Finally, a commenter laments the shift away from such low-level approaches in favor of higher-level libraries and languages. They express concern that the underlying principles and mechanics of image processing might be obscured by these abstractions, potentially hindering a deeper understanding of the field. This comment suggests that the book remains relevant for those who want to grasp the foundational elements of image processing, even in today's landscape dominated by higher-level tools.
The overall tone of the comments is respectful and appreciative of the book's value, particularly for educational purposes and historical context. While acknowledging the advancements in image processing techniques and tools, the commenters recognize the importance of understanding the fundamental principles presented in the book.