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POwhy gradient colors and aliasing under Lion are different compare to Snow Leopard?
 

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  1. POwhy gradient colors and aliasing under Lion are different compare to Snow Leopard?
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    <p>Just came across one weird problem. I generate programmatically a gradient inside round cornered square like so:</p> <pre><code>CGColorSpaceRef colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceAdobeRGB1998); CGContextRef mcontext = [[NSGraphicsContext currentContext] graphicsPort]; size_t capacityBarGradientNumLocations = 11; CGGradientRef Gradient; CGFloat capacityBarGradientLocations[11] = { /* skipped */ }; CGFloat capacityBarGradientColors[44] = { /* skipped */ }; Gradient = CGGradientCreateWithColorComponents (colorSpace, capacityBarGradientColors, capacityBarGradientLocations, capacityBarGradientNumLocations); CGContextDrawLinearGradient(mcontext,Gradient, CGPointMake(0,baroffset), CGPointMake(0,barheight+baroffset), 0); </code></pre> <p>I've just noticed that the same code produces completely different results between Lion and Snow Leopard on the same mac (I have a dual boot) and monitor with the same color profiles. Please take a look at the screenshot: <img src="https://i.stack.imgur.com/q4v8P.png" alt="Weird gradient problem under Lion"></p> <p>Left part if taken under Lion, the right one - under Snow Leopard. How can I fix my gradient appearance under Lion? </p> <p>Some extra info regarding the above picture. I've used a black color with variable alpha to generate semi transparent gradient i.e:</p> <pre><code>CGFloat capacityBarGradientColors[44] = { 0.0, 0.0, 0.0, .65, 0.0, 0.0, 0.0, .35, /* skipped */ 0.0, 0.0, 0.0, .35, 0.0, 0.0, 0.0, .65, }; </code></pre> <p>I thought maybe there is something wrong with the way i use alpha. Decided to use actual colors with Multiply blending mode and alpha set to 1.0 :</p> <pre><code>CGFloat capacityBarGradientColors[44] = { 0x59/255., 0x59/255., 0x59/255., 1.0, 0xa6/255., 0xa6/255., 0xa6/255., 1.0, /* skipped */ 0xa6/255., 0xa6/255., 0xa6/255., 1.0, 0x59/255., 0x59/255., 0x59/255., 1.0, }; </code></pre> <p>Under Snow Leopard I've got the result I've been looking for. But under Lion I've got completely different picture. take a look at the screenshot: <img src="https://i.stack.imgur.com/F3RDb.png" alt="lion blending mode problem"></p> <p>Left - Lion, right - Snow Leopard</p> <p>Here is the code changes I did:</p> <pre><code>Gradient = CGGradientCreateWithColorComponents (colorSpace, capacityBarGradientColors, capacityBarGradientLocations, capacityBarGradientNumLocations); CGContextSetBlendMode(mcontext, kCGBlendModeMultiply); CGContextDrawLinearGradient(mcontext,Gradient, CGPointMake(0,baroffset), CGPointMake(0,barheight+baroffset), 0); CGContextSetBlendMode(mcontext, kCGBlendModeNormal); </code></pre>
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    1. USGrAnD
    1. USGrAnD
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      1. POwhy gradient colors and aliasing under Lion are different compare to Snow Leopard?
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    1. COCould you attach sample app?
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      1. POwhy gradient colors and aliasing under Lion are different compare to Snow Leopard?
      1. USKentzo
    2. COAfter a few hours going through the code I've tracked down a problem to a CGContextSetShadowWithColor call earlier in the code on a view where I create my gradients. I've replaced the shadow with a gradient and that resolved the problem. The question still stands though... Why the same code produces different results between Lion and Snow Leopard?
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      1. POwhy gradient colors and aliasing under Lion are different compare to Snow Leopard?
      1. USGrAnD
    3. COI think you're doing something wrong so the behavior is undefined. I'd like to see all code in a sample project.
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      1. POwhy gradient colors and aliasing under Lion are different compare to Snow Leopard?
      1. USKentzo
 

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