如何在 iPhone 上读取 RGB 像素数据

Question

我想知道如何在 iPhone 上扫描图像并分析每个像素的 RGB 值，从而最终确定整个图像的平均 RGB。如果有人能把我推向正确的方向，将不胜感激。我是图像分析的新手，不知道从哪里开始，或者 iOS 5 API 中是否包含类似的东西。

Answer 1

粘贴即可，我正在检测触摸颜色。

- (void) touchesEnded:(NSSet*)touches withEvent:(UIEvent*)event {

if (self.view.hidden==YES) {
    //color wheel is hidden, so don't handle  this as a color wheel event.
    [[self nextResponder] touchesEnded:touches withEvent:event];
    return;
}

UITouch* touch = [touches anyObject];
CGPoint point = [touch locationInView:self.view]; //where image was tapped
UIColor * lastColor = [self getPixelColorAtLocation:point];
NSLog(@"color %@",lastColor);
UIImageView *lbl=[[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];
lbl.layer.cornerRadius=50;
[imageView addSubview:lbl];
lbl.backgroundColor=lastColor;
lbl.center=CGPointMake(stillImageFilter.center.x*320, (stillImageFilter.center.y*320)-125);
NSLog(@"stillImageCenter = %f,%f",stillImageFilter.center.x,stillImageFilter.center.y);}

- (UIColor*) getPixelColorAtLocation:(CGPoint)point {
UIColor* color = nil;
CGImageRef inImage = imageView.image.CGImage;

CGContextRef cgctx = [self createARGBBitmapContextFromImage:inImage];
if (cgctx == NULL) { return nil; /* error */ }

size_t w = CGImageGetWidth(inImage);
size_t h = CGImageGetHeight(inImage);
CGRect rect = {{0,0},{w,h}};


CGContextDrawImage(cgctx, rect, inImage);


unsigned char* data = CGBitmapContextGetData (cgctx);
if (data != NULL) {

    int offset = 4*((w*round(point.y))+round(point.x));
    int alpha =  data[offset];
    int red = data[offset+1];
    int green = data[offset+2];
    int blue = data[offset+3];
    NSLog(@"offset: %i colors: RGB A %i %i %i  %i",offset,red,green,blue,alpha);
    color = [UIColor colorWithRed:(red/255.0f) green:(green/255.0f) blue:(blue/255.0f) alpha:(alpha/255.0f)];
}


CGContextRelease(cgctx);

if (data) { free(data); }

return color;

}

- (CGContextRef) createARGBBitmapContextFromImage:(CGImageRef) inImage {

CGContextRef    context = NULL;
CGColorSpaceRef colorSpace;
void *          bitmapData;
int             bitmapByteCount;
int             bitmapBytesPerRow;


size_t pixelsWide = CGImageGetWidth(inImage);
size_t pixelsHigh = CGImageGetHeight(inImage);


bitmapBytesPerRow   = (pixelsWide * 4);
bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh);


colorSpace = CGColorSpaceCreateDeviceRGB();

if (colorSpace == NULL)
{
    fprintf(stderr, "Error allocating color space\n");
    return NULL;
}


bitmapData = malloc( bitmapByteCount );
if (bitmapData == NULL)
{
    fprintf (stderr, "Memory not allocated!");
    CGColorSpaceRelease( colorSpace );
    return NULL;
}


context = CGBitmapContextCreate (bitmapData,
                                 pixelsWide,
                                 pixelsHigh,
                                 8,      // bits per component
                                 bitmapBytesPerRow,
                                 colorSpace,
                                 kCGImageAlphaPremultipliedFirst);
if (context == NULL)
{
    free (bitmapData);
    fprintf (stderr, "Context not created!");
}


CGColorSpaceRelease( colorSpace );

return context;

}

Answer 2

查看Camera Programming Topics for iOS - Taking Pictures and Movies，这将在您的应用中获取图像。

然后看看类似的东西：how-to-get-the-rgb-values-for-a-pixel-on-an-image-on-the-iphone

Answer 3

从 UIImage 获取 CGImage 可以为您提供这些数据

CFDataRef pixelData = CGDataProviderCopyData(CGImageGetDataProvider(image.CGImage));
const UInt8* data = CFDataGetBytePtr(pixelData);

int pixelInfo = ((image.size.width  * y) + x ) * 4; // The image is png

UInt8 red = data[pixelInfo];         
UInt8 green = data[(pixelInfo + 1)]; 
UInt8 blue = data[pixelInfo + 2];    
UInt8 alpha = data[pixelInfo + 3];     
CFRelease(pixelData);

更多： Getting pixel data from UIImageView -- works on simulator, not device

这里：Get Pixel color of UIImage