ios - Get screen (View) black pixels fast and efficiently -


i searching in asked questions, of them describing how pixel colour of uiimage (which did not best solution in case).

i want check pixels of screen , number of black pixels or black (very dark) pixels. know how check how dark single pixel - checking if rgb (255) values of pixel selected less 10 or something. don't know how check full amount of pixels of uiimage in fast , efficient way.

so want check pixels of screen , number of them. later in app again , compare amount of black pixels before , after events.

is there fast solution them?

it "snapshot" searching if else have similar situation. took snapshot:

 uigraphicsbeginimagecontext(self.view.bounds.size);  [self.view.layer renderincontext:uigraphicsgetcurrentcontext()];  uiimage *original = uigraphicsgetimagefromcurrentimagecontext();  uigraphicsendimagecontext();

and searched black pixels in it:

    width = (int)original.size.width;     height = (int)original.size.height;       cfdataref imagedata = cgdataprovidercopydata(cgimagegetdataprovider(original.cgimage));       const uint8 *pixels = cfdatagetbyteptr(imagedata);     uint8 blackthreshold = 5; // or value close 0 - dark pixels     int bytesperpixel = 4;        for(int x = 0; x < width; x++) {         for(int y = 0; y < height; y++) {            int pixelstartindex = (x + (y * width)) * bytesperpixel;          uint8 redvalue= pixels[pixelstartindex];         uint8 greenvalue = pixels[pixelstartindex + 1];         uint8 bluevalue = pixels[pixelstartindex + 2];  if(redvalue < blackthreshold && bluevalue < blackthreshold && greenvalue < blackthreshold) {             /// count black pixels ore else want         }     } }

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