iPhones now have four LEDs to produce the flash light.
I want to programatically turn each LED on or off to produce different light effects, or even just specify the balance between pink LEDs and white leds.
Any way to have a tighter control on those in swift ?
Digging the API didn't show much...
Thanks !!
Related
Video demonstration (please watch, 18s): https://youtu.be/4HtkadKEnWM
When I reduce the brightness of the device, iOS seems to be changing white to off-white. For my use case, it is important that the view background is actually white so the video appears to seamlessly blend into the background. Interestingly, when I take a screenshot or screen recording this effect does not appear.
I am on light mode and don't have any custom color space settings.
Does anyone have any ideas on how to fix this? Thank you!
You have a misunderstanding of colours.
White doesn't really exist, but it is defined as (non-specular) reflection of standard illumination (ISO standard about paper say nearly 90% of reflection).
So white depends on brightness, so with the same light, you can see black, grey, white, or super-white. Just out eyes adapt quickly to a reference white.
For emissive devices, this is more tricky because emission doesn't depend on ambient light. For this reason, since years we have some sort of ambient light detection, so that software can tell screen to reduce brightness (or/and to change white balance [in this case "white balance" is about colours, not brightness).
If one person dim the screen, probably it is because it has less ambient light, and such person is not seeing white correctly. In any case, the eyes (and brain) will adapt quickly.
In short: white is a uniform colour at maximum brightness. if you dim the screen, it will appear grey for a short amount of time, because we had a different idea of maximum brightness. but we adapt.
Note: we have two adaptation: brightness and colours. Good filmakers may use it for good, but also colourists must handle it (on long grey scenes, not to make us to adapt and see it white).
Note: hardware may have two kind of brightness: one, the classic done by RGB, and one about global brightness (the backlight, also if now there is not more backlight). If you save screenshot, it takes just the RGB, and not the corrected values. But also if you take a photo, every cameras check the brightness, and automatically expose the photo (the average brightness of an image should be rendered as mid-grey). So also in this case you see no differences (if you really want to see it, you should set your camera in manual exposition mode, and take the two photos with same setting).
After communicating with Apple support, we discovered that the video_full_range_flag was not being set by ffmpeg. Re-encoding the videos using the following ffmpeg command worked: ffmpeg -i input.mp4 -map 0 -c copy -bsf:v h264_metadata=video_full_range_flag=1 output.mp4.
When I test my unity 2D game on my iPhone X, all background and sprite elements on the screen have a blue "halo" when moving my character. I have explored the issue with transparency on mobile, but the issue seems really strange. The blue halo appears only when the background is black. Anything brighter and it is absolutely fine. So I doubt it's a transparency issue given that it appears only when a dark background is present.
It is visible only on mobile, so taking a screenshot is useless.
If anyone wants to test do the following. Download or open the image attached here to full screen. Zoom in just a bit so the shapes are taking most of the screen. Start moving the image left and right. Slow and fast and you should see a blueish after-image around the edges. This should happen only on some OLED mobile screens.
If anyone ever encounters this. The result I mentioned is an after-image effect from the OLED screen on the iPhone X. I haven't tested on other OLED devices, but I assume depending on the software it is possible other models can experience this. The levels of Black are incredible, but when you have a high contrast situation between light and dark, an after-image is created around the edges of the contrast zone.
How to fix this?
Simply do not use full black backgrounds or elements. Near black colors in a game situation is indistinguishable from a true black, 0, 0, 0 RGB, choice. This might be a common game design principle I am unaware of and I am the only person stupid enough to use 0,0,0 in the first place, but anyway, I hope if someone has the same issue to read this and fix it easily,
I am writing a script on the raspberry pi to detect the majority colour featured in a frame of a webcam and I seem to be having an issue. The following image is me holding up my phone with a blank red image on it. I seem to be getting an orange colour instead.
Now when I angle the phone I do in fact produce the red colour expected.
I am not sure why this is the case.
I am using a logitech c920 webcam that emits a blue light when activated and also have the monitor going. I am wondering whether the light from these two are causing this issue and when I angle it, these lights are not hitting it front on and thus not distributing the image.
I am still not heavily experienced in this area so I would enjoy hearing explanations and possible work arounds for my problem.
Thanks
There are a few things that can mess this up:
As you already mention, the light from the monitor and the camera.
The iPhone screen is a display, so flicker and sync might also be coming to play.
Reflection from the iPhone screen.
If your camera has automatic control for exposure and color balance etc., the picture quality can change as you move around.
I suggest using a colored piece of non-glossy paper so that you can remove the iPhone display's effects.
in an iOS application I need to recognize colors through camera, but analyzing the problem, I noticed that different kinds of light make the colors observed in the captured picture a little bit different from the real ones. For example, under a high neon light a light blue seems like a gray.
What is the cause and what kind of approch I could follow to solve this problem of "fake colors"?
The colors are not fake, they are just different than what you expect them to be. As #Piglet said this has a lot to do with the physics of light and white balance may help.
If you want to read more about it look at:
Color Rendering Index
Color Metamerism
Sensitivity Metamerism Index
Color Constancy
These all refer to the physics behind why different illuminations create different colors. There is also the camera color pipeline that contributes its share, so you can also read about white balance and tone mapping...
I'm trying to work on an iOS app that turns off the screen (so that when you are in the dark, it doesn't show any light at all), but I can turn on and off certain pixels of the screen.
Does anyone know a way to do this? I am assuming that it's either all or nothing... Either turn off all the screen, or turn it all on, but maybe someone knows better?
I am guessing that the best I could do is turn the background black so that as little light as possible comes through. However, I tried this using my iPad and it still generates too much light in a pitch black room. I want for instance, only 1 pixel to shine brightly, and the rest to not glow at all. And if this is not possible, is there any way to mimic this?
As far as I'm aware the screen is either on or off, there's no controller for setting specific regions to on/off.
Also you can't change the pixel level brightness, as the screen isn't illuminated that way. You can only control the overall screen brightness, not each pixel, as the screen lighting technology doesn't work that way, it's specifically an LED backlight.
I'm afraid I agree with #garretmurray. What you're trying to do just isn't possible. You're on the best track though.
You can change the background color of the view you're on to black, and use the following to kill the screen's brightness:
[[UIScreen mainScreen] setBrightness:0.0f];
What you're trying to do is not possible.