IOS implements code that takes color from the background image _ios

This article explains the iOS from the background Image color code, shared for everyone to refer to, the specific contents are as follows

Implementation code:

void *bitmapdata;
 
A pointer to the memory space equal to the number of bytes used by the image to use the RGB channel.
  Static Cgcontextref Creatergbabitmapcontext (Cgimageref inimage) {cgcontextref context = NULL;
  Cgcolorspaceref ColorSpace;
  int bitmapbytecount;
 
  int bitmapbytesperrow; size_t pixelswide = Cgimagegetwidth (inimage);
 
  Gets the number of horizontal pixels size_t Pixelshigh = cgimagegetheight (inimage); Bitmapbytesperrow = (Pixelswide * 4); The number of bytes in each row is occupied by the pixel, and each pixel ARGB four channels each occupy 8 bit (0-255) of space Bitmapbytecount = (Bitmapbytesperrow * pixelshigh); Calculates the number of bytes occupied by an entire graph ColorSpace = Cgcolorspacecreatedevicergb ()//Create a device-dependent RGB channel/memory space allocated enough to hold the number of pictures bytes BitmapData = malloc (b
  Itmapbytecount);
                   Creates a coregraphic graphics context that describes some of the drawing parameters of the image that the bitmadata points to in the memory space need to be drawn in the context = Cgbitmapcontextcreate (BitmapData,
                   Pixelswide, Pixelshigh, 8, Bitmapbytesperrow,
  ColorSpace, Kcgimagealphapremultipliedlast); In the Core Foundation, a pointer created by the name of the method containing the Create, alloc, is required to use the CFRelease () function releases cgcolorspacerelease (colorspace);
return context; //Returns a pointer to an array in which each of the four elements in the array is the RGBA value of a pixel on the image (0-255), with unsigned char because its exact range of values is 0-255 static unsigned char *
  Requestimagepixeldata (UIImage *inimage) {cgimageref img = [Inimage cgimage];
  Cgsize size = [inimage size];
  Use the above function to create context cgcontextref CGCTX = Creatergbabitmapcontext (IMG);
  CGRect rect = {{0,0},{size.width, size.height}};
  Draws the target image to the specified context, which is actually the bitmapdata within the context.
  Cgcontextdrawimage (CGCTX, Rect, IMG);
  unsigned char *data = Cgbitmapcontextgetdata (CGCTX);
  Releases the context cgcontextrelease (CGCTX) created by the above function;
return data;
  //Set Background picture--(void) Setsourceimage: (NSString *) sourceimage imagewidth: (int) _width imageheight: (int) _height {
  Generates a background figure of the specified size uiimage *im = [UIImage imagenamed:sourceimage];
  UIImage *newimage;
  Uiimageview *view = [[Uiimageview alloc] initwithimage:im];
  View.frame = CGRectMake (0, 0, _width, _height); Uigraphicsbeginimagecontext (Cgsizemake (_width, _height)); Size is Cgsize classType, that is, the picture size you need [im Drawinrect:cgrectmake (0, 0, _width, _height)];
  NEWIMAGERECT Specifies the picture drawing area NewImage = Uigraphicsgetimagefromcurrentimagecontext ();
 
  Uigraphicsendimagecontext ();
  width = newImage.size.width;
  Height = newImage.size.height;
The analytic background image is pixel, and the Imgpixel = Requestimagepixeldata (newimage) is used for color extraction.  }//Calculation color-(uicolor*) Calcolor: (cgpoint) apoint {int i = 4 * Width * ROUND (APOINT.Y+IMAGEVIEW.FRAME.SIZE.HEIGHT/2) + 4 *
  Round (APOINT.X+IMAGEVIEW.FRAME.SIZE.WIDTH/2);
  int _r = (unsigned char) imgpixel[i];
  int _g = (unsigned char) imgpixel[i+1];
  int _b = (unsigned char) imgpixel[i+2];
  NSLog (@ "(%f,%f)", APOINT.X,APOINT.Y);
  NSLog (@ "Red:%f Green:%f Blue:%f", _r/255.0,_g/255.0,_b/255.0);
return [Uicolor colorwithred:_r/255.0f green:_g/255.0f blue:_b/255.0f alpha:1.0];
  }-(void) Changcolor: (Uicolor *) color{int width_; if (![
  Util Isipad]) {width_ = 30;
  else {width_ = 70;
  } uigraphicsbeginimagecontext (Cgsizemake (Width_, width_)); Cgcontextref Ctx = Uigraphicsgetcurrentcontext ();
  Cgcontextmovetopoint (CTX, 20, 20); Cgcontextsetfillcolorwithcolor (CTX, color.
  Cgcolor); if (![
  Util Isipad]) {Cgcontextaddarc (CTX, WIDTH_/2, WIDTH_/2, 14.5, 0, 6.3, 0);
  else {Cgcontextaddarc (CTX, width_/2+0.5, WIDTH_/2, 31.3, 0, 6.3, 0);
  } cgcontextfillpath (CTX);
  Self->pickedcolorimageview.image = Uigraphicsgetimagefromcurrentimagecontext ();
Uigraphicsendimagecontext ();
 }

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