alpha

Why does the UISlider view ignore the alpha view when set to 0.5? Code: for (int i = 0; i < 3; i++) { UISlider *slider = [[[UISlider alloc] initWithFrame:CGRectMake(0, i * 30, 200, 30)] autorelease]; slider.alpha = 0.4 + (CGFloat)i / 10.0f; [window addSubview:slider]; } Result: The sliders have alpha values 0.4, 0.5 and 0.6. And as you can see the middle one with 0.5 is completely opaque. It seams to only occur with alpha 0.5. Have tested other UI controllers and they work as expected with alpha is set to 0.5. Reproduced with iOS 4.2 on real device and with iOS 3.2 and 4.2 in simulator. BTW if

占坑 来源： https://www.cnblogs.com/huangzp1104/p/11795301.html

I would like to know the difference between: Assigning my UIView a color with <1 alpha vs Assigning it a non-transparent color but giving the UIView a <1 alpha value. On the screenshot I have made two UIViews with two black (alpha = 1.0) UILabels on top of each: Assume a macro _RGB is defined before: #define _RGB(r,g,b,a) [UIColor colorWithRed:r/255.0 green:g/255.0 blue:b/255.0 alpha:a] and then here is the code:: [_view1 setBackgroundColor:_RGB(255, 0, 0, 1)]; [_view1 setAlpha:0.5]; [_view2 setBackgroundColor:_RGB(255, 0, 0, 0.5)]; [_view2 setAlpha:1]; [_view3 setBackgroundColor:_RGB(255, 0,

I was trying to code up some color manipulation code and was stuck for a long time with alpha, then I (2 hours later) realized browsers render rgba differently. I created this test: http://jsbin.com/adekez/2/ add /edit to look at the code Here are the results in 4 browsers in OSX Lion: http://imgur.com/g2iqu That is an element with a background of rgba(0,0,0,0.5) on top of white. My hex calculator says: FF÷2 = 7F.8 which means Safari at #808080 is correct Firefox at #7F7F7F is off by 1 Opera at #7E7E7E is off by 2 Chrome at #929292 is way off What's going here, is this a bug in Chrome or do I

There are a couple similar questions on SO, but none of them really helped. Basically I am trying to resize a simple png image, as seen here: http://media.spiralknights.com/wiki-images/3/3e/Equipment-Proto_Sword_icon.png (from the mmo Spiral Knights, copyright Three Rings Entertainment) I had originally implemented a utility which uses these images in php, and the resizing utility there worked perfectly well. I used the method described on the imagecopyresampled page in PHP's documentation. Honestly I can't even get it to resize better in Photoshop, but the results are almost disastrous in

This question already has answers here : UIView: opaque vs. alpha vs. opacity (2 answers) I want to use animation to change UIView's color to make it fade, however, somehow i can't access and set opacity, but i can set alpha. I wonder if alpha and opacity are the same? Search on the web and I didnt find a good answer. Thanks a lot for your help! alex Actually "opacity" means "value of alpha-channel" of your UIView . When a view is fully opaque this means its alpha = 1 , when a view is fully transparent (non-opaque) its alpha = 0 . As about properties of CALayer and UIView in Cocoa, yes, they

I am trying to merge two videos together, both have transparency, using the command ffmpeg.exe -i person2.mov -vf "[in] scale=iw/2:ih/2,fade=out:300:30:alpha=1, pad=2*iw:ih [left]; movie=person2.mov, scale=iw/2:ih/2,fade=out:300:30:alpha=1 [right]; [left][right] overlay=main_w/3:0,fade=out:300:30:alpha=1 [out]" -b:v 768k Output_people.mov By doing that I get the following output: http://i263.photobucket.com/albums/ii122/Fernando461/Untitled.png As you can see, it was possible to get the two videos to be on top of each other. But then, when I try to merge this video (Output_people.mov) with