ios - Swift 3 CGContext 内存泄漏
<p><p>我正在使用 CGBitMapContext() 将颜色空间转换为 ARGB 并获取像素数据值，我为位图上下文分配空间并在完成后释放它，但我仍然在仪器中看到内存泄漏我想我可能做错了什么，所以任何帮助都将不胜感激。 </p>
<p>这里是 ARGBBitmapContext 函数</p>
<pre><code>func createARGBBitmapContext(width: Int, height: Int) -> CGContext {
var bitmapByteCount = 0
var bitmapBytesPerRow = 0
//Get image width, height
let pixelsWide = width
let pixelsHigh = height
bitmapBytesPerRow = Int(pixelsWide) * 4
bitmapByteCount = bitmapBytesPerRow * Int(pixelsHigh)
let colorSpace = CGColorSpaceCreateDeviceRGB()
// Here is the malloc call that Instruments complains of
let bitmapData = malloc(bitmapByteCount)
let context = CGContext(data: bitmapData, width: pixelsWide, height: pixelsHigh, bitsPerComponent: 8, bytesPerRow: bitmapBytesPerRow, space: colorSpace, bitmapInfo: CGImageAlphaInfo.premultipliedFirst.rawValue)
// Do I need to free something here first?
return context!
}
</code></pre>
<p>这里是我使用上下文检索所有像素值作为 UInt8 列表的地方(以及内存泄漏的地方)</p>
<pre><code>extension UIImage {
func ARGBPixelValues() -> {
let width = Int(self.size.width)
let height = Int(self.size.height)
var pixels = (repeatElement(0, count: width * height * 3))
let rect = CGRect(x: 0, y: 0, width: width, height: height)
let context = createARGBBitmapContext(inImage: self.cgImage!)
context.clear(rect)
context.draw(self.cgImage!, in: rect)
var location = 0
if let data = context.data {
while location < (width * height) {
let arrOffset = 3 * location
let offset = 4 * (location)
let R = data.load(fromByteOffset: offset + 1, as: UInt8.self)
let G = data.load(fromByteOffset: offset + 2, as: UInt8.self)
let B = data.load(fromByteOffset: offset + 3, as: UInt8.self)
pixels = R
pixels = G
pixels = B
location += 1
}
free(context.data) // Free the data consumed, perhaps this isn't right?
}
return pixels
}
}
</code></pre>
<p>Instruments 报告了 1.48MiB 的 malloc 错误，这适合我的图像大小 (540 x 720) 我释放了数据，但显然这不正确。 </p>
<p>我应该提一下，我知道你可以将 nil 传递给 CGContext init(它会管理内存)，但我更好奇为什么使用 malloc 会产生问题，我应该知道更多的东西(我更熟悉 Obj -C)。</p></p>
<br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
<p><p>因为 CoreGraphics 不是由 ARC 处理的(就像所有其他 C 库一样)，所以即使在 Swift 中，您也需要使用自动释放来包装您的代码。特别是如果您不在主线程上(如果涉及 CoreGraphics，您不应该在主线程上...... .userInitiated 或更低是合适的)。</p>
<pre><code>func myFunc() {
for _ in 0 ..< makeMoneyFast {
autoreleasepool {
// Create CGImageRef etc...
// Do Stuff... whir... whiz... PROFIT!
}
}
}
</code></pre>
<p>对于那些关心的人，你的 Objective-C 也应该像这样包装:</p>
<pre><code>BOOL result = NO;
NSMutableData* data = [ init];
@autoreleasepool {
CGImageRef image = [self CGImageWithResolution:dpi
hasAlpha:hasAlpha
relativeScale:scale];
NSAssert(image != nil, @"could not create image for TIFF export");
if (image == nil)
return nil;
CGImageDestinationRef destRef = CGImageDestinationCreateWithData((CFMutableDataRef)data, kUTTypeTIFF, 1, NULL);
CGImageDestinationAddImage(destRef, image, (CFDictionaryRef)options);
result = CGImageDestinationFinalize(destRef);
CFRelease(destRef);
}
if (result) {
return ;
} else {
return nil;
}
</code></pre>
<p>见 <a href="https://stackoverflow.com/questions/25860942/is-it-necessary-to-use-autoreleasepool-in-a-swift-program" rel="noreferrer noopener nofollow">this answer</a>了解详情。</p></p>
<p style="font-size: 20px;">关于ios - Swift 3 CGContext 内存泄漏，我们在Stack Overflow上找到一个类似的问题：
<a href="https://stackoverflow.com/questions/43339784/" rel="noreferrer noopener nofollow" style="color: red;">
https://stackoverflow.com/questions/43339784/
</a>
</p>
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