I'm building this to run on the Mac, not iOS - which is quit different. I'm almost there with the speedo, but the math of making the needle move up and down the scale as data is input eludes me. I'm measuring wind speed live, and want to display it as a gauge - speedometer, with the needle moving as the windspeed changes. I have the fundamentals ok. I can also - and will - load the images into holders, but later. For now I want to get it working ...
- (void)drawRect:(NSRect)rect
{
NSRect myRect = NSMakeRect ( 21, 21, 323, 325 ); // set the Graphics class square size to match the guage image
[[NSColor blueColor] set]; // colour it in in blue - just because you can...
NSRectFill ( myRect );
[[NSGraphicsContext currentContext] // set up the graphics context
setImageInterpolation: NSImageInterpolationHigh]; // highres image
//-------------------------------------------
NSSize viewSize = [self bounds].size;
NSSize imageSize = { 320, 322 }; // the actual image rectangle size. You can scale the image here if you like. x and y remember
NSPoint viewCenter;
viewCenter.x = viewSize.width * 0.50; // set the view center, both x & y
viewCenter.y = viewSize.height * 0.50;
NSPoint imageOrigin = viewCenter;
imageOrigin.x -= imageSize.width * 0.50; // set the origin of the first point
imageOrigin.y -= imageSize.height * 0.50;
NSRect destRect;
destRect.origin = imageOrigin; // set the image origin
destRect.size = imageSize; // and size
NSString * file = @"/Users/robert/Documents/XCode Projects/xWeather Graphics/Gauge_mph_320x322.png"; // stuff in the image
NSImage * image = [[NSImage alloc] initWithContentsOfFile:file];
//-------------------------------------------
NSSize view2Size = [self bounds].size;
NSSize image2Size = { 149, 17 }; // the orange needle
NSPoint view2Center;
view2Center.x = view2Size.width * 0.50; // set the view center, both x & y
view2Center.y = view2Size.height * 0.50;
NSPoint image2Origin = view2Center;
//image2Origin.x -= image2Size.width * 0.50; // set the origin of the first point
image2Origin.x = 47;
image2Origin.y -= image2Size.height * 0.50;
NSRect dest2Rect;
dest2Rect.origin = image2Origin; // set the image origin
dest2Rect.size = image2Size; // and size now is needle size
NSString * file2 = @"/Users/robert/Documents/XCode Projects/xWeather Graphics/orange-needle01.png";
NSImage * image2 = [[NSImage alloc] initWithContentsOfFile:file2];
// do image 1
[image setFlipped:YES]; // flip it because everything else is in this exerecise
// do image 2
[image2 setFlipped:YES]; // flip it because everything else is in this exerecise
[image drawInRect: destRect
fromRect: NSZeroRect
operation: NSCompositeSourceOver
fraction: 1.0];
[image2 drawInRect: dest2Rect
fromRect: NSZeroRect
operation: NSCompositeSourceOver
fraction: 1.0];
NSBezierPath * path = [NSBezierPath bezierPathWithRect:destRect]; // draw a red border around the whole thing
[path setLineWidth:3];
[[NSColor redColor] set];
[path stroke];
}
// flip the ocords - (BOOL) isFlipped { return YES; }
@end
The result is here. The gauge part that is. Now all I have to do is make the needle move in response to input.
Apple has some sample code, called SpeedometerView, which does exactly what you're asking. It'll surely take some doing to adapt it for your use, but it's probably a decent starting point.
