got a question about turning pixels off on a screen. I can make a black image and show it full screen on my pc. Yet the screen looks black but the pixels aren't off. You can see the difference between an off screen and a black screen.
I am wordering if it would be possible to turn these pixels off via a program or is the best you can do: make them black?
I am looking for the delphi code to turn off the right half of my computer screen?
hope its clear!
thx
You can't turn off individual pixels, or parts of the screen. Either the screen is on or it's off.
This works a bit differently depending on what kind of screen it is, but nowadays LCD screens is the most common kind. An LCD screen has a backlight behind an LCD display; the backlight is always on, and shine through the LCD display when the crystals are transparent. Pixels are made black by making the crystals non-transparent, however they still let a fraction of the back light through. To make pixels completely black you would have to turn the backlight off, and you can only to that for the entire screen.
If I get it right, you want to turn off the power from the half of your monitor, what is impossible. It would have to be supported by your graphic card as well as by your monitor driver.
Turning off pixels can only work on new all-lead displays, except if you are switching off the computer, when all systems (including the screen) are off.
Related
Lets assume my home screen have UIView that is 80% black in color. Does this help to save battery? I know backlight of iPhone will on no matter what is the screen color is. But having more black pixels make the battery less stressful?
Thats true for OLED displays only, but it's LCD display in iPhone. So answer - black screen will not save you battery.
If you make a simple website with the code:
<div style='background-color: rgba(0,0,0,.05);width:50px;height:50px'></div>
and view it on various devices, you'll see very different colors.
On my iPhone and iPad, it looks white but on my MacBook you can see a definite light grey that looks close to #fafafa; I haven't tested thoroughly on other devices but I think that Android Chrome will sometimes display a third in between color.
This isn't an issue of different screen color capacities, because the iPad is definitely capable of displaying #fafafa.
So what's the story and is there any way to fix it?
rgba(0,0,0,.05) is an incredibly light color. A 5% tint is not visible on many lower end LCDs - especially 6bit panels. Personally, when I use RGBA I only tweak by 10% increments. Also, you will notice that #fafafa and rgba(0,0,0,.05) don't display the same because they aren't the same. #f2f2f2 is rgba(0,0,0,.05) (at least in Photoshop.)
You also have variances between the type of RGB. Devices also adapt differently based on lighting conditions - and they don't adapt the same way. There's also different screen types like AMOLED
From my experience that normally happens because of the contrast on the different screens and brightness settings. My suggestion is play with those.
Also check this for browser compatibility but those you mentioned should be ok:
http://css-tricks.com/rgba-browser-support/
Is there a way to clip objects in "letterbox" scaling mode? I can add black rectangles over the areas that I want to appear as clipped, but actual clipping should have a performance benefit. Is it possible?
No, there are no way to do actual manual culling.
On my company we also use black rectangles.
Corona culling, and there are no way to control it from our side, and it cull automatically everything outside the screen. In letterbox mode things in the "black" area of the letterbox are still inside the screen, thus they are not culled.
I'm using a full screen UIWebView to house/render an HTML5 application under iOS. Very much like Cordova/phonegap although I'm not using those. I try to make my webview size match the underlying display. Unfortunately, on retina displays, the value returned by self.view.bounds relies on the UIScreen scaling factor. So I get 1024x768 instead of 2048x1536. Not a huge problem except I then instantiate the UIWebView using the smaller bounds (after adjusting for the status bar) and some things get a bit jaggy. In particular, I use canvas at a couple of points and also rounded borders appear thick. To be clear, this isn't a case of scaled raster resources.
I'm not getting the full resolution of the screen using that UIWebView. Ideally, I'd like to set the screen scale to 1.0 but that doesn't appear to be supported. Any suggestions on how best to get full advantage of the screen?
The problem is most noticeable on the iPhone 5 simulator. I don't have that hardware to test on. iPad/new iPad I think has the problem but the jaggies aren't as noticeable.
Update: The more I look at this, the more I think it may be restricted to canvas.
Solution: In case anyone else gets here. Based on the answer below, I created all of my canvas elements with width and height multiplied by window.devicePixelRatio and then set their style attribute to have the original (device independent) size.
See https://stackoverflow.com/a/7736803/341994. Basically you need to detect that you've got double resolution and effectively double the resolution of the canvas.
I'm using UIImagePickerController in a popover on the iPad to take a picture with the front camera. I set allowsEditing to YES and get the awesome built in "Move and Scale" view after taking the picture. The crop rectangle in this view measures 320x267 on the screen despite the fact that the image is cropped to a 320x320 square (http://dl.dropbox.com/u/2246698/moveAndScale.png). If i accept the image as is without resizing or moving it, there is a ~25px high black bar across the top as if the crop rectangle has been positioned too high on the image (http://dl.dropbox.com/u/2246698/cropped.png). In fact, if i get that crop rectangle from the media info dictionary (via UIImagePickerControllerCropRect) it shows that the y origin of the crop rectangle is at -39. This seems broken that the image would be incorrectly cropped by default and usually when it seems broken it's because i did it wrong. Has anyone ever seen this or know of some setting to twiddle that will be good for my crops?
Many thanks.
I see the exact same behavior. It MUST be a bug, but if it is, I don't know why more people aren't complaining about it. Another problem with it is that you can't move the picture to the edges to crop to include that part--it always slides back to the middle.
If you zoom it, then you can move it, but you can never move it far enough to be able to include the left or right edges.
The thing is next to useless.