我正在开发一个进行图像处理并显示结果图像的应用程序。我UIScrollView用来让用户滚动所有图像，因为图像不是标准的 jpg 或 png，加载需要时间。我使用 GCD 异步加载，当完成调度到主队列以显示时。片段如下：
- (void)loadImage:(NSString *)name
{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
UIImage *image = [Reader loadImage:name];
dispatch_sync(dispatch_get_main_queue(), ^{
[self displayImage:image];
});
});
}
Reader的loadImage方法是这样的：
+ (UIImage *)loadImage:(NSString *)name
{
UInt8 *data = NULL;
NSString *mfjPath = [TMP stringByAppendingPathComponent:name];
NSData *mfjData = [NSData dataWithContentsOfFile:mfjPath];
if(mfjData){
data = malloc(sizeof(UInt8)*mfjData.length);
[mfjData getBytes:data];
}
if(data){
ResultHolder *result = [sDecoder decodeData:data withOffset:0];// static id<IDecoder> sDecoder; in Reader.m before @implementation Reader.
return [result bitmap];
}
retun nil;
}
IDCoder是一个协议，它是
@protocol IDecoder <NSObject>
- (ResultHolder *)decodeData:(UInt8 *) withOffset:(int)offset;
@end
ResultHolder是一个加载简单图像和组合复杂图像的类。如下：
ResultHolder.h
typedef struct color24{
UInt8 R;
UInt8 G;
UInt8 B;
} Color24;
@interface ResultHolder : NSObject
{
unsigned long mWidth;
unsigned long mHeight;
UInt8 *mData;
CGImageRef mBitmap;
BOOL isMonoColor;
Color24 mMonoColor;
}
+ (ResultHolder *)resultHolderWithCGImage:(CGImageRef)image;
+ (ResultHolder *)resultHolderWithData:(UInt8 *)data Width:(unsigned long)width andHeight:(unsigned long)height;
+ (ResultHolder *)resultHolderWithMonoColor:(Color24)monoColor withWidth:(unsigned long)width andHeight:(unsigned long)height;
- (ResultHolder *)initWithData:(UInt8 *)data Width:(unsigned long)width andHeight:(unsigned long) height;
- (ResultHolder *)initWithCGImage:(CGImageRef)image;
- (ResultHolder *)initWithMonoColor:(Color24)monoColor withWidth:(unsigned long)width andHeight:(unsigned long)height;
- (BOOL)isSuccess;
- (UIImage *)bitmap;
- (void)combineFixResultHolder:(ResultHolder *)child Rect:(CGRect)bounds Width:(unsigned long)width andHeight:(unsigned long)height;
- (void)combineResultHolder:(ResultHolder *)child Bounds:(CGRect)bounds Width:(unsigned long)width andHeight:(unsigned long)height;
@end
ResultHolder.m
@implementation ResultHolder
@synthesize width = mWidth;
@synthesize height = mHeight;
@synthesize isMonoColor;
@synthesize monoColor = mMonoColor;
- (ResultHolder *)initWithData:(UInt8 *)data Width:(unsigned long)width andHeight:(unsigned long)height
{
if (self = [super init]) {
mWidth = width;
mHeight = height;
mData = malloc(mWidth*mHeight*sizeof(Color24));
memcpy(mData, data, mWidth*mHeight*sizeof(Color24));
mBitmap = NULL;
}
return self;
}
- (ResultHolder *)initWithCGImage:(CGImageRef)image
{
if (self = [super init]) {
mBitmap = CGImageRetain(image);
mWidth = CGImageGetWidth(image);
mHeight = CGImageGetHeight(image);
}
return self;
}
- (ResultHolder *)initWithMonoColor:(Color24)monoColor withWidth:(unsigned long)width andHeight:(unsigned long)height
{
if (self = [super init]) {
mMonoColor = monoColor;
isMonoColor = YES;
mWidth = width;
mHeight = height;
mBitmap = NULL;
mData = NULL;
}
return self;
}
+ (ResultHolder *)resultHolderWithCGImage:(CGImageRef)image
{
ResultHolder *resultHolder = [[ResultHolder alloc] initWithCGImage:image];
return resultHolder;
}
+ (ResultHolder *)resultHolderWithData:(UInt8 *)data Width:(unsigned long)width andHeight:(unsigned long)height
{
ResultHolder *resultHolder = [[ResultHolder alloc] initWithData:data Width:width andHeight:height];
return resultHolder;
}
+ (ResultHolder *)resultHolderWithMonoColor:(Color24)monoColor withWidth:(unsigned long)width andHeight:(unsigned long)height
{
ResultHolder *resultHolder = [[ResultHolder alloc] initWithMonoColor:monoColor withWidth:width andHeight:height];
return resultHolder;
}
- (BOOL)isSuccess
{
if ([ReaderConfigures CodecDebug])
NSLog(@"ResultHolder isSuccess");
return (mData != NULL || isMonoColor || mBitmap != nil);
}
- (void)fillMonoColor
{
if (isMonoColor) {
if (mData) {
free(mData);
}
mData = (UInt8 *)malloc(mWidth*mHeight*sizeof(Color24));
for (int i = 0; i < mHeight; i++) {
for (int j = 0; j < mWidth; j++) {
memcpy(mData+(i*mWidth+j)*3, &mMonoColor, sizeof(Color24));
}
}
isMonoColor = NO;
}
}
- (void)extractBitmap
{
if (mBitmap) {
CGDataProviderRef dataProvider = CGImageGetDataProvider(mBitmap);
CFDataRef bitmapData = CGDataProviderCopyData(dataProvider);
UInt8 * dataSource = (UInt8 *)CFDataGetBytePtr(bitmapData);
size_t width = CGImageGetWidth(mBitmap);
size_t height = CGImageGetHeight(mBitmap);
if(mData)
free(mData);
mData = malloc(width*height*3);
for (int i = 0; i < height; i++) {
for (int j = 0; j < width; j++) {
memcpy(mData+(i*width+j)*3, dataSource+(i*width+j)*4, sizeof(Color24));
}
}
CFRelease(bitmapData);
CGImageRelease(mBitmap);
mBitmap = NULL;
}
}
- (UInt8 *)getRawData
{
if (mBitmap) {
[self extractBitmap];
}
if (isMonoColor) {
[self fillMonoColor];
}
return mData;
}
- (UIImage *)bitmap
{
if (mBitmap) {
UIImage *image = [[UIImage alloc] initWithCGImage:mBitmap];
CGImageRelease(mBitmap);
mBitmap = NULL;
return image;
}
if (isMonoColor) {
[self fillMonoColor];
}
if (mData) {
CGDataProviderRef dataProvider = CGDataProviderCreateWithData(NULL, mData, mWidth*mHeight*3, NULL);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGImageRef bitmap = CGImageCreate(mWidth, mHeight, 8, 24, mWidth*3, colorSpace, kCGBitmapByteOrderDefault, dataProvider, NULL, YES, kCGRenderingIntentDefault);
CGColorSpaceRelease(colorSpace);
CGDataProviderRelease(dataProvider);
UIImage *image = [[UIImage alloc] initWithCGImage:bitmap];
CGImageRelease(bitmap);
return image;
}
return nil;
}
- (void)combineResultHolder:(ResultHolder *) child Bounds:(CGRect) bounds Width:(unsigned long)width andHeight:(unsigned long)height
{
CGRect rect = CGRectMake(MAX(0, bounds.origin.x), MAX(0, bounds.origin.y),MIN(width - 1, bounds.origin.x + bounds.size.width), MIN(height - 1, bounds.origin.y + bounds.size.height));
int w = MIN(rect.size.width + 1, child.width);
int h = MIN(rect.size.height + 1, child.height);
int dstPos = (height - 1 - (rect.origin.y + h - 1))*width;
UInt8 *dataParent = [self getRawData];
if (child.isMonoColor) {
Color24 childMonoColor = child.monoColor;
for (int i = 0; i < h; i++) {
memcpy(dataParent+(dstPos+(int)rect.origin.x)*3, &childMonoColor, w*3);
dstPos += width;
}
} else {
UInt8 *dataChild = [child getRawData];
if (dataChild != nil) {
int srcPos = 0;
for (int i = 0; i < h; i++) {
memcpy(dataParent+dstPos*3+((int)rect.origin.x)*3, dataChild+srcPos*3, w*3);
srcPos += child.width;
dstPos += width;
}
}
}
}
- (void)combineFixResultHolder:(ResultHolder *)child Rect:(CGRect)bounds Width:(unsigned long)width andHeight:(unsigned long)height
{
CGRect rect = CGRectMake(bounds.origin.x, height-1-bounds.origin.y-bounds.size.height, bounds.origin.x+bounds.size.width, height-1-bounds.origin.y);
[self combineResultHolder:child Bounds:rect Width:width andHeight:height];
}
- (void)dealloc
{
if (mData) {
free(mData);
mData = NULL;
}
if (mBitmap) {
CGImageRelease(mBitmap);
mBitmap = NULL;
}
}
@end
对于简单的图像，例如仅 JPEG 图像， + (ResultHolder *)resultHolderWithCGImage:(CGImageRef)image;并- (UIImage *)bitmap;调用方法。对于一些复杂的，
会ResultHolder提取mBitmap到mData，然后结合 sub得到图像。如果我在主线程中加载图像，这些方法效果很好，但是如果我使用 GCD 或在后台加载图像，则很容易崩溃，尤其是在后台加载复杂的图像时。当应用程序崩溃时，主线程状态为 CGSConvertBGR888toRGBA8888 方法错误，其他线程之一正在运行该方法，实际上是. 加载线程和主线程之间似乎存在内存冲突。resultHoldermDataNSThread[ResultHolder dealloc]free(mData)
当应用程序崩溃时，错误是这样的：
我为这个错误苦苦挣扎了好几天，但仍然找不到解决方法。我希望有人能帮助我。任何建议表示赞赏。
更新：我制作了一个演示项目ReaderDemo来模拟这种情况。有兴趣的可以下载看看错误。这个项目有15张图片，5,7,14张图片会在滚动的时候导致crash，比其他的稍微复杂一些。但是如果您滚动缩略图滚动视图然后单击，它们都可以显示。