我使用這段代碼來縮放和旋轉使用照片相機拍攝的圖像。當我使用這個時,我可以看到一個巨大的記憶峯值。像20 MB。當我使用這些工具時,我可以看到這一行:巨大的內存峯值 - CGContextDrawImage
CGContextDrawImage(ctxt,orig,self.CGImage);
包含20 MB。這是正常的全分辨率的照片? iPhone 4S可以處理它。但由於此代碼,較舊的設備崩潰。
我重新調整圖像後,我需要它在NSData中,所以我使用UIImageJPEGRepresentation()方法。這一起使記憶峯值更高。它在內存使用上達到70 MB,持續幾秒鐘。
是的,我讀了幾乎所有關於內存使用情況的iOS相機相關問題。但沒有答案。
// WBImage.mm -- extra UIImage methods
// by allen brunson march 29 2009
#include "WBImage.h"
static inline CGFloat degreesToRadians(CGFloat degrees)
{
return M_PI * (degrees/180.0);
}
static inline CGSize swapWidthAndHeight(CGSize size)
{
CGFloat swap = size.width;
size.width = size.height;
size.height = swap;
return size;
}
@implementation UIImage (WBImage)
// rotate an image to any 90-degree orientation, with or without mirroring.
// original code by kevin lohman, heavily modified by yours truly.
// http://blog.logichigh.com/2008/06/05/uiimage-fix/
-(UIImage*)rotate:(UIImageOrientation)orient
{
CGRect bnds = CGRectZero;
UIImage* copy = nil;
CGContextRef ctxt = nil;
CGRect rect = CGRectZero;
CGAffineTransform tran = CGAffineTransformIdentity;
bnds.size = self.size;
rect.size = self.size;
switch (orient)
{
case UIImageOrientationUp:
return self;
case UIImageOrientationUpMirrored:
tran = CGAffineTransformMakeTranslation(rect.size.width, 0.0);
tran = CGAffineTransformScale(tran, -1.0, 1.0);
break;
case UIImageOrientationDown:
tran = CGAffineTransformMakeTranslation(rect.size.width,
rect.size.height);
tran = CGAffineTransformRotate(tran, degreesToRadians(180.0));
break;
case UIImageOrientationDownMirrored:
tran = CGAffineTransformMakeTranslation(0.0, rect.size.height);
tran = CGAffineTransformScale(tran, 1.0, -1.0);
break;
case UIImageOrientationLeft:
bnds.size = swapWidthAndHeight(bnds.size);
tran = CGAffineTransformMakeTranslation(0.0, rect.size.width);
tran = CGAffineTransformRotate(tran, degreesToRadians(-90.0));
break;
case UIImageOrientationLeftMirrored:
bnds.size = swapWidthAndHeight(bnds.size);
tran = CGAffineTransformMakeTranslation(rect.size.height,
rect.size.width);
tran = CGAffineTransformScale(tran, -1.0, 1.0);
tran = CGAffineTransformRotate(tran, degreesToRadians(-90.0));
break;
case UIImageOrientationRight:
bnds.size = swapWidthAndHeight(bnds.size);
tran = CGAffineTransformMakeTranslation(rect.size.height, 0.0);
tran = CGAffineTransformRotate(tran, degreesToRadians(90.0));
break;
case UIImageOrientationRightMirrored:
bnds.size = swapWidthAndHeight(bnds.size);
tran = CGAffineTransformMakeScale(-1.0, 1.0);
tran = CGAffineTransformRotate(tran, degreesToRadians(90.0));
break;
default:
// orientation value supplied is invalid
assert(false);
return nil;
}
UIGraphicsBeginImageContext(rect.size);
ctxt = UIGraphicsGetCurrentContext();
switch (orient)
{
case UIImageOrientationLeft:
case UIImageOrientationLeftMirrored:
case UIImageOrientationRight:
case UIImageOrientationRightMirrored:
CGContextScaleCTM(ctxt, -1.0, 1.0);
CGContextTranslateCTM(ctxt, -rect.size.height, 0.0);
break;
default:
CGContextScaleCTM(ctxt, 1.0, -1.0);
CGContextTranslateCTM(ctxt, 0.0, -rect.size.height);
break;
}
CGContextConcatCTM(ctxt, tran);
CGContextDrawImage(ctxt, bnds, self.CGImage);
copy = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return copy;
}
-(UIImage*)rotateAndScaleFromCameraWithMaxSize:(CGFloat)maxSize
{
UIImage* imag = self;
imag = [imag rotate:imag.imageOrientation];
imag = [imag scaleWithMaxSize:maxSize];
return imag;
}
-(UIImage*)scaleWithMaxSize:(CGFloat)maxSize
{
return [self scaleWithMaxSize:maxSize quality:kCGInterpolationHigh];
}
-(UIImage*)scaleWithMaxSize:(CGFloat)maxSize
quality:(CGInterpolationQuality)quality
{
CGRect bnds = CGRectZero;
UIImage* copy = nil;
CGContextRef ctxt = nil;
CGRect orig = CGRectZero;
CGFloat rtio = 0.0;
CGFloat scal = 1.0;
bnds.size = self.size;
orig.size = self.size;
rtio = orig.size.width/orig.size.height;
if ((orig.size.width <= maxSize) && (orig.size.height <= maxSize))
{
return self;
}
if (rtio > 1.0)
{
bnds.size.width = maxSize;
bnds.size.height = maxSize/rtio;
}
else
{
bnds.size.width = maxSize * rtio;
bnds.size.height = maxSize;
}
UIGraphicsBeginImageContext(bnds.size);
ctxt = UIGraphicsGetCurrentContext();
scal = bnds.size.width/orig.size.width;
CGContextSetInterpolationQuality(ctxt, quality);
CGContextScaleCTM(ctxt, scal, -scal);
CGContextTranslateCTM(ctxt, 0.0, -orig.size.height);
CGContextDrawImage(ctxt, orig, self.CGImage);
copy = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return copy;
}
@end
謝謝!這幫了很多忙。 – timthetoolman 2012-06-30 06:14:45