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All blog entries, ordered from most recent. Entry count: 1032.
3 Rules to Make You Image Looking Good on a Projector
As I go to conferences (and sometimes present my slides), do music visualizations on parties and attend demoscene parties, I started noticing what looks good and what doesn't when presented on a big screen using a projector. It's often not the same thing as you expect when preparing your content and see it on a monitor. The problem is that while monitors usually do pretty good job in representing all shades of colors and brightnesses and we adjust them to see the image from the right distance and in good lighting conditions, with image presented from a projector it's often not the case. You never know what to expect from the quality of the image before you actually enter the venue where you are going to present. That's why I have prepared three simple rules to follow if you want your content to look good on a projector:
1. Use High Contrast
White (or almost white) objects on black background are OK. Black (or almost black) objects on white background are also OK. Gray objects on gray background are not OK. In other words: don't rely on subtle differences in brightness.
Why? Because they may not be visible on the big screen. Sometimes the projector is not powerful enough to ensure sufficient contrast and so everything looks very dark. Sometimes the lighting conditions are such that everything looks very bright. Sometimes the gamma of the image is very different than you experience when preparing your content. (By gamma, I basically mean the curve showing how perceived brightness depends on the brightness value of a pixel.) As a result, all the dark colors may be indistinguishable and completely black, or all the bright colors may be indistinguishable and completely white, or conversely - small difference in pixel brightness can make large difference on the big screen.
So basically use high contrast for all your images. Using subtle differences in pixel brightness for adding some details is OK, but make sure the image looks good and conveys all the key information also without them, relying only on the difference between black and white.
2. Don't Rely on Colors
Monitors can represent most of the colors from sRGB space more or less correctly, but you shouldn't expect the same from a projector. Some colors may seem brighter or darker than expected. Sometimes colors just look completely different on the big screen.
That's why you shouldn't rely on them. Showing some details using colors is OK, but make sure your image looks good and conveys all the key information also without them, relying on brightness alone.
I can remember watching a business presentation where some data was shown on a graph using a yellow line on white background. It was completely invisible on the big screen, so the presenter turned his laptop for us so we could see it. Another time I needed to present on a screen that was lit by a blue lamp and there was no way to turn it off. All parts of the image looked more or less blue and there was no point in using any colors. I even seen a situation where one of RGB components didn't work at all because of the broken cable!
3. Use Big Objects
Use only large font size, prefer big objects of uniform brightness/color and make all lines thick. Don't show any important things as small objects or characters and don't use single-pixel width lines.
Why? Because they may not be readable or visible at all. Sometimes the screen is too small or some viewers sit too far from it. Some people have bad vision and might forget their glasses. Sometimes the image gets downscaled. Many projectors have low resolution. The image quality may just be bad - for example long VGA (D-sub) cable introduces some horizontal blur. I sometimes connect my laptop to a HDMI video switcher that presents itself to the laptop as Full HD (1080p) display, while its output is actually connected to a projector having native resolution of 1024 x 768. I once needed to present on an old projector that didn't have either D-sub or HDMI input, only Composite, S-Video and... a DVD player. Not only I needed a special converter, but also image quality was very bad because standard definition PAL TV signal is only 576i.
For good examples, see demos from Cocoon group (see the group on pouet.net, search YouTube). I think they are not only masterpiece of both technology and art, but they are also deliberately prepared to look great on a big screen by following the rules similar to what I described here.
Nonbreaking Space and No-Width Optional Break
Wrapping text on word boundaries instead of single character boundaries is a great invention. A text looks so much better when inserted to Word:
Than when printed in oldschool console:
But there are places where we may not want a line break to be possible despite we insert a space. For example, in Europe we use space as thousand separator (and comma as decimal mark) when writing down numbers.
A special character called "nonbreaking space" is very helpful in such cases. You can insert it in Word by clicking: Insert > Symbol > More Symbols > Special Characters > Nonbreaking space. This character looks like space, but it doesn't cause line break.
You can actually see this "invisible" character when you press Ctrl+*. It looks like a small circle or a degree sign.
In HTML you can specify a non-breaking space as:
I have discovered quite recently that there is also an opposite special character, called "no-width optional break" or "zero-width space". It is useful in cases where you have a long sequence of characters (like a file path) and you want it to be broken across lines despite it doesn't contain any spaces. It is especially important when you use text justification, because such a long text moved to separate line as a whole can cause an ugly effect:
You can insert this special character in Word (e.g. after every backspace in the path) by clicking: Insert > Symbols > More Symbols > Special Characters > No-width optional break. It occupies no space, but it tells the word processor that a line can be broken at this point. Now it looks much better:
When you press Ctrl+*, you can see this special character depicted as a rectangle.
In HTML you can also use it by typing:
​. It's Unicode "Zero Width Space" character.
Operator New and Delete - Unnecessary Conditions
I've seen following constructs many times in C++ code:
MyClass* obj = new MyClass();
if(obj == nullptr)
// Handle allocation error.
if(obj != nullptr)
Both of these conditions are unnecessary. Strictly speaking they are not a bug - program will run correctly, but they make no sense. If you used to write any of these, you should know that:
new doesn't return null on failed allocation. By default it throws an exception of type
std::bad_alloc in this case, so this is what you should handle if you really care about the state of your program after it runs out of memory (or if the allocated object is particularly big).
There is also special
nothrow version of the
new operator that returns null on failure, but you must call it explicitly. An alternative would be to overload
new operator (global or for particular class) to change its behavior. But again, this is not what happens by default.
Note this is different behavior than
malloc function from C. Obviously there are no exceptions in C language, so this function just returns null on failure.
delete doesn't crash when you pass null pointer to it - it just does nothing, so the check for not-null is already inside, you don't have to write it. Of course trying to delete object from any non-null address that was already freed or is just invalid address still crashes, or causes other undefined behavior.
Note this is the same behavior as
free function from C - it also accepts null pointer.
32-bit Applications on 64-bit Windows
As you probably know, the processor, operating system and applications on a PC may be 32-bit or 64-bit. CPU-s we have in our computers are 64-bit for a long time already. Windows XP tended to be used in 32-bit version, but now I can see most people use Windows 7/8/8.1/10 in 64-bit version as well. Only apps still exist in various forms. Shell extensions and drivers must match the version of the operating system, but other programs can be used in 32-bit version even on 64-bit system. Different combinations are possible:
We may ask a question about where does Windows store files and settings of such apps. It is especially interesting as the answer is very counter-intuitive. Location for (2) – 64-bit apps on 64-bit Windows – may contain “32” in its name (because of backward compatibility), while location for (3) – 32-bit apps on 64-bit Windows – may contain “64” (because of the name WoW64). Here is the list of such locations:
Program Files folder:
(Same applies to HKEY_CURRENT_USER.)
Color Temperature of Your Lighting
In photography, video and all graphics in general there are so much more parameters to consider than just exposure, meaning lighter or darker image. One of them is color temperature, or white balance. It's about what we consider "white" - a frame of reference, especially concerning light source and so all the objects lit by it. It's not real temperature, but we measure it in Kelvins. Paradoxically, lower color temperature values (like 3000K) mean colors that we call "warmer" - more towards yellow, orange or red. Higher temeratures (like 7000K) mean "cooler" colors - more towards blue. Values like 6500K are considered equivalent of a sunlight during the day, while light bulbs usually have around 3000K. Color temperature of your lighting is important when you work with colors on a computer. They recommend to use 6500K light source for that purpose.
I decided to make an experiment. Below you can see photos of part of my room, with a test screen displayed on my monitor, piece of my wall (behind it, supposed to be white) and a piece of furniture (the right part, also should be white). The monitor is LG 23MA73D-PZ, with IPS panel, calibrated to what I believe should be around 6500K (setting Colour Temperature = Warm2).
Left column shows a photo taken in the middle of the night, with lighting by LED lamps having 3000K color temperature. Middle column is the same scene lit by different LED lamps having 6500K. Finally, right column show a photo taken during the day, using only sunlight.
The only remainig variable is white balance of the photo itself. That's why I introduced two rows. Top row show all three photos calibrated to same white balance = 6500K. As you can see, the image on the screen looks pretty much the same on all of them, because monitor emits its own light. But the wall and the furniture, lit by a specific light source, seems orange or reddish on the first photo, while on the other photos it's more or less gray.
Our eyes, as well as cameras can adjust to changing color temperature to compensate for it and make everything looking neutral-white again. So the second row shows same photos calibrated to white balance of the specific light source. Now the wall and the furniture looks neutral gray on all of them, but notice what happened with the image on the screen when light was 3000K - it completely changed colors of the picture, making everything looking blue.
That's why it's so important to consider color temperature of your light sources when working with color correction and grading of photos, videos or some other graphics. Otherwise you can produce an image that looked good at the time of making, but turns out to have some color cast when seen under different lighting conditions. Of course, if you just work with text or code, it doesn't matter that much. It is more important then to just have a pleasant lighting that doesn't cause eye strain, which would probably be something more like the 3000K lamps.
How to Boost Your RAM to Declared 3000 MHz?
I recently upgraded some components of my desktop PC. I was suprised to discover that RAM doesn't work with declared speed of 3000 MHz. Here is the solution I've found to this problem.
Back in the days of DOS I can remember having to set up everything manually, like selecting IRQ number and DMA channel to make sound working in games. But today, in the era of Plug&Play, assembling a computer is easy and everything works automatically. Almost everything...
Although I found that both my new motherboard (Gigabyte GA-Z170-HD3P) and RAM modules (Corsair Vengeance LPX DDR4, 32GB(2x16GB), 3000MHz, CL15 (CMK32GX4M2B3000C15)) support 3000 MHz frequency, it worked on 2133 MHz. Motherboard specification says: "Support for DDR4 3466(O.C.) /3400(O.C.) /3333(O.C.) /3300(O.C.) /3200(O.C.) /3000(O.C.) /2800(O.C.) /2666(O.C.) /2400(O.C.) /2133 MHz memory modules", while specification of the memory has "3000MHz" even in its title. What happened? Motherboard spec calling all the frequencies higher than 2133 "OC" (like in "overclocking") gave me some clue that it is not standard.
After few minutes of searching on Google, I've learn about a thing called XMP (Extreme Memory Profile). It's an extension to SPD (Serial Presence Detect) - a protocol used by RAM modules to report to the motherboard what parameters do they support. I then checked in the specs that my motherboard, as well as my memory support XMP 2.0.
So what I finally did was:
That's all! Fortunately I didn't need to manually set any frequency, timings or voltage of my Skylake processor, memory or any other components, like overclockers do. With all the other settings left to default "Auto", the computer still works stable and RAM now runs with 3000 MHz frequency.
By the way: Please don't be worried when you see only half of this frequency in HWiNFO64 tool as "Memory - Current Memory Clock". All in all we are talking about DDR here, which means "Double Data Rate", so the real frequency is just that, but data is transferred on both rising and falling edge of the clock signal.
Warning! It turned out that enabling XMP on my machine makes it working very unstable. Firefox, The Witcher 3 and basically all memory-intensive applications crashed randomly. So if you experience similar issues, you better disable XMP or, if you know any better solution, please post a comment about it.
Internet in Poland - My History
This article at forbes.pl says that yesterday there was a 26-th anniversary of first Internet connection in Poland. On 26 September 1990 scientists made a first connection between Warsaw and Geneva to transfer some data. I thought it might be a good opportunity to write down some memories of my personal beginnings with the Internet. I think it can be interesting to some younger readers that know only the modern Internet as it looks today, as well as to some foreigners, because history of the Internet it other countries may be a little bit different than in Poland.
I know there were things before, like people dialing specific numbers and connecting to so called BBS-es, but my first experiences were already dealing with "this" global Internet. I was in high school back then. At first I started to go to Internet cafes - venues throughout the city where you paid per hours you could spend working on a computer connected to the global network, and possibly downloading some files to your floppy disks. Going there after (or instead of :) school, I first learned how to use IRC and of course WWW. IRC was a protocol that required a client app (mIRC was the most popular one for Windows) and allowed to chat with people, privately or on numerous topic channels, so it was possible e.g. to meet local girls in my city :)
Of course the Web existed already too, with many pages about programming that I've been reading to learn Delphi and download some new components for it. There was no all-knowing Google then, not to mention StackOverflow. Instead there were multiple competing search engines (e.g. Yahoo, AltaVista, Infoseek, Lycos, HotBot) and their algorithms were not so good yet. Page directories were also popular, with manually managed lists of websites grouped into categories and subcategories. Many people created websites about the topics of their interest, like "John's website about programming", or about fishing, or whatever. Pages looked different than today. Their style was to be later called "Web 1.0", with the use of HTML frames, textured backgrounds and animated GIF-s.
Pitfalls of Floating-Point Numbers - Slides
Here you can find slides from my presentation, in Polish. It's called "Pu³apki liczb zmiennoprzecinkowych" ("Pitfalls of floating-point numbers").
Here are links to the Floating-Point Formats Cheatsheet (in English) that I mentioned in my presentation: