有时我们会用到获取点击某一点的颜色或者RGB，就好比，控制灯的颜色，一个颜色板，点击颜色板上的红色，灯就会变红，这个时候我们就会使用到。下面就是实现方法
原理，首先获取一张屏幕截图，在获取截图上面的颜色。
1 获取屏幕截图，但不是真的会截图，只是生成了一个Image对象
```
/**
获取屏幕截图
@return 返回屏幕截图
*/
-(UIImage *)fullScreenshots{
UIWindow *screenWindow = [[UIApplication sharedApplication] keyWindow];
UIGraphicsBeginImageContext(screenWindow.frame.size);//全屏截图，包括window
[screenWindow.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
return viewImage;
}
```
2 接下来就是获取颜色和RGB
``
/**
获取点击的颜色
@param point 点击的位置
@return 返回点击地方的颜色
*/
- (UIColor*) getPixelColorAtLocation:(CGPoint)point withImage:(UIImage*) image {
UIColor* color = nil;
CGImageRef inImage = image.CGImage;
// Create off screen bitmap context to draw the image into. Format ARGB is 4 bytes for each pixel: Alpa, Red, Green, Blue
CGContextRef cgctx = [self createARGBBitmapContextFromImage:inImage];
if (cgctx == NULL) { return nil; }
size_t w = CGImageGetWidth(inImage);
size_t h = CGImageGetHeight(inImage);
CGRect rect = {{0,0},{w,h}};
// Draw the image to the bitmap context. Once we draw, the memory
// allocated for the context for rendering will then contain the
// raw image data in the specified color space.
CGContextDrawImage(cgctx, rect, inImage);
// Now we can get a pointer to the image data associated with the bitmap
// context.
unsigned char* data = CGBitmapContextGetData (cgctx);
if (data != NULL) {
//offset locates the pixel in the data from x,y.
//4 for 4 bytes of data per pixel, w is width of one row of data.
@try {
int offset = 4*((w*round(point.y))+round(point.x));
NSLog(@"offset: %d", offset);
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)];
}
@catch (NSException * e) {
NSLog(@"%@",[e reason]);
}
@finally {
}
}
return color;
}
- (CGContextRef) createARGBBitmapContextFromImage:(CGImageRef) inImage {
CGContextRef context = NULL;
CGColorSpaceRef colorSpace;
void * bitmapData;
int bitmapByteCount;
int bitmapBytesPerRow;
// Get image width, height. We'll use the entire image.
size_t pixelsWide = CGImageGetWidth(inImage);
size_t pixelsHigh = CGImageGetHeight(inImage);
// Declare the number of bytes per row. Each pixel in the bitmap in this
// example is represented by 4 bytes; 8 bits each of red, green, blue, and
// alpha.
bitmapBytesPerRow = (pixelsWide * 4);
bitmapByteCount = (bitmapBytesPerRow * pixelsHigh);
// Use the generic RGB color space.
colorSpace = CGColorSpaceCreateDeviceRGB();
if (colorSpace == NULL)
{
fprintf(stderr, "Error allocating color spacen");
return NULL;
}
// Allocate memory for image data. This is the destination in memory
// where any drawing to the bitmap context will be rendered.
bitmapData = malloc( bitmapByteCount );
if (bitmapData == NULL)
{
fprintf (stderr, "Memory not allocated!");
CGColorSpaceRelease( colorSpace );
return NULL;
}
// Create the bitmap context. We want pre-multiplied ARGB, 8-bits
// per component. Regardless of what the source image format is
// (CMYK, Grayscale, and so on) it will be converted over to the format
// specified here by CGBitmapContextCreate.
context = CGBitmapContextCreate (bitmapData,
pixelsWide,
pixelsHigh,
8, // bits per component
bitmapBytesPerRow,
colorSpace,
kCGImageAlphaPremultipliedFirst);
if (context == NULL)
{
free (bitmapData);
fprintf (stderr, "Context not created!");
}
// Make sure and release colorspace before returning
CGColorSpaceRelease( colorSpace );
return context;
}
```
这样就获取了颜色以及对应打印的RGB
3 如何使用
//点击获取点击位置的颜色
-(IBAction)onClik:(UITapGestureRecognizer*)tap{
CGPoint point = [tap locationInView:self];
UIColor* color = [self getPixelColorAtLocation:point withImage:[self fullScreenshots]];
}
这样就完成了，点击任意一个位置，就可以获取对应的颜色和RGB
