Multi tool use

Draw a bitmap picture on IOS based on a set of RGB data

I'd like to draw a bimap picture on IOS platform based on a set of RGB data but I got some problems when referring to this official web: https://developer.apple.com/library/archive/documentation/GraphicsImaging/Conceptual/drawingwithquartz2d/dq_images/dq_images.html#//apple_ref/doc/uid/TP30001066-CH212-TPXREF101

The biggest problem here for me is that The tutorial drew a bitmap picture on MAC OS while not on IOS.

SO, I added a subview to the view and intended to draw the bitmap picture on the subview.

UIImageView *imgview = [[UIImageView alloc] initWithFrame:CGRectMake(15, 355, 384, 288)];
[self drawBitmap:384 andPixelshigh:288];
[self.view addSubview:imgview];


The drawBitmap function is a self-written function used to draw the bitmap following the tutorial.

- (void)drawBitmap:(NSInteger)pixelsWide andPixelshigh: (NSInteger)pixelsHigh{
CGRect myBoundingBox;
CGContextRef myBitmapContext;
CGImageRef myImage;

myBoundingBox = CGRectMake (33, 366, 384, 288);
myBitmapContext = [self MyCreateBitmapContext:pixelsWide andPixelsHigh:pixelsHigh];
CGContextSetRGBFillColor (myBitmapContext, 1, 0, 0, 1);
CGContextFillRect (myBitmapContext, CGRectMake (100, 100, 200, 100 ));
CGContextSetRGBFillColor (myBitmapContext, 0, 0, 1, .5);
CGContextFillRect (myBitmapContext, CGRectMake (100, 100, 100, 200 ));
myImage = CGBitmapContextCreateImage (myBitmapContext);
CGContextDrawImage(myBitmapContext, myBoundingBox, myImage);
char *bitmapData = CGBitmapContextGetData(myBitmapContext);
CGContextRelease (myBitmapContext);
if (bitmapData)
free(bitmapData);
CGImageRelease(myImage);
}


and myBitmapContext is the context of the bitmap picture generated by the following function.

- (CGContextRef) MyCreateBitmapContext: (NSInteger) pixelsWide andPixelsHigh: (NSInteger) pixelsHigh{
CGContextRef context = NULL;
CGColorSpaceRef colorSpace;
NSInteger * bitmapData;
NSInteger bitmapByteCount;
NSInteger bitmapBytesPerRow;

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

colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
bitmapData = (NSInteger *)calloc( bitmapByteCount, sizeof(uint8_t) );
if (bitmapData == NULL)
{
return NULL;
}
context = CGBitmapContextCreate (bitmapData,
pixelsWide,
pixelsHigh,
8,
bitmapBytesPerRow,
colorSpace,
kCGImageAlphaPremultipliedLast);
if (context== NULL)
{
free (bitmapData);
return NULL;
}
CGColorSpaceRelease( colorSpace );

return context;
}


I think there's nothing wrong with my code but I just can't draw the bitmap figure I want.

2 Answers
2

How about UIImage(data: imageData) in swift or [UIImage imageWithData:imageData] in Objective-C

UIImage(data: imageData)

[UIImage imageWithData:imageData]

I suddenly realized that I made a very stupid mistake. The function CGBitmapContextCreateImage() has its return value, which is actually a UIImage. So the solution to this problem is just to assign the return value to myView.image to show the image.

CGBitmapContextCreateImage()

UIImage

myView.image

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