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我正在尝试将像素动态插入到 PNG 图像文件中，并尝试在不更改使用下面代码保存的像素的情况下将其取回。但我这样做并不成功。有人可以帮我指出问题出在哪里吗？谢谢。

// Original pixels for debugging only
NSString *sPixels = @"12345678";
const char *cpPixels8 = sPixels.UTF8String;

char *cpPixelsStore = calloc(sPixels.length + 1, 1);
strncpy(cpPixelsStore, cpPixels8, sPixels.length);

unsigned int r,g,b,a;
for(int j = 0; j < sPixels.length; j += 4)
{
    r = cpPixelsStore[j+0];
    g = cpPixelsStore[j+1];
    b = cpPixelsStore[j+2];
    a = cpPixelsStore[j+3];

    printf("r:0x%X g:0x%X b:0x%X a:0x%X\n", r, g, b, a);
}

int width = 2;
int height = 1;
int bytesPerRow = 4 * width;
int bitsPerComponent = 8;
int bitsPerPixel = 32;

CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = kCGBitmapByteOrder32Host | kCGImageAlphaLast;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;

CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, cpPixelsStore, (bytesPerRow * height), NULL);

CGImageRef imRef = CGImageCreate(width, height, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);

CGDataProviderRelease(provider);

UIImage *imNewTemp = [UIImage imageWithCGImage:imRef];
NSData *datPNG = UIImagePNGRepresentation(imNewTemp);

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *sFile = [documentsDirectory stringByAppendingPathComponent:@"Pic.png"];

[datPNG writeToFile:sFile atomically:YES];

CGImageRelease(imRef);

// Cross verify save
UIImage *imTemp = [UIImage imageWithContentsOfFile:sFile];
NSData *datImagePixels = (__bridge NSData *)CGDataProviderCopyData(CGImageGetDataProvider(imTemp.CGImage));
unsigned char *ucpPixelBytes = (unsigned char *)[datImagePixels bytes];

for(int j = 0; j < datImagePixels.length; j += 4)
{
    r = ucpPixelBytes[j+0];
    g = ucpPixelBytes[j+1];
    b = ucpPixelBytes[j+2];
    a = ucpPixelBytes[j+3];

    printf("r:0x%X g:0x%X b:0x%X a:0x%X\n", r, g, b, a);
}

初始 printf 在创建过程中返回： r:0x31 g:0x32 b:0x33 a:0x34 r:0x35 g:0x36 b:0x37 a:0x38

保存和检索文件后的 printf 给出以下输出： r:0xA g:0xA b:0xA a:0x31 r:0xC g:0xB b:0xB a:0x35

我迷失在翻译中。请帮忙。

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1 回答 1

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NSData 是不可变的——你需要一个 NSMutableData 对象，然后你使用“mutableBytes”来获取指针。NSMutableData *nData = [NSMutableData dataWithData:datImagePixels];

现在您有了数据来创建带有修改的新图像。您可以使用 Quartz 方法 CGImageCreate() 来获取 CGImageRef，并从中获取 UIImage。

于 2012-08-21T23:06:47.050 回答