i know common question , there lot of answers of question. i've used of this. although many of them same. sad thing me none of them worked me. following codes i've used till now.
-(void)getrgbasfromimage:(uiimage*)image atx:(int)xx andy:(int)yy { // first image data buffer cgimageref imageref = [image cgimage]; nsuinteger width = cgimagegetwidth(imageref); nsuinteger height = cgimagegetheight(imageref); cgcolorspaceref colorspace = cgcolorspacecreatedevicergb(); unsigned char *rawdata = (unsigned char*) calloc(height * width * 4, sizeof(unsigned char)); nsuinteger bytesperpixel = 4; nsuinteger bytesperrow = bytesperpixel * width; nsuinteger bitspercomponent = 8; cgcontextref context = cgbitmapcontextcreate(rawdata, width, height, bitspercomponent, bytesperrow, colorspace, kcgimagealphapremultipliedlast | kcgbitmapbyteorder32big); cgcolorspacerelease(colorspace); cgcontextdrawimage(context, cgrectmake(0, 0, width, height), imageref); cgcontextrelease(context); // rawdata contains image data in rgba8888 pixel format. int byteindex = (bytesperrow * yy) + xx * bytesperpixel; cgfloat red = (rawdata[byteindex] * 1.0) / 255.0; cgfloat green = (rawdata[byteindex + 1] * 1.0) / 255.0; cgfloat blue = (rawdata[byteindex + 2] * 1.0) / 255.0; cgfloat alpha = (rawdata[byteindex + 3] * 1.0) / 255.0; byteindex += 4; nslog(@"the vale of rbg of red %f",red); democolor.tintcolor = [uicolor colorwithred:red green:green blue:blue alpha:alpha]; free(rawdata); } here approach i've used -
- (cgcontextref) createargbbitmapcontextfromimage:(cgimageref) inimage { cgcontextref context = null; cgcolorspaceref colorspace; void * bitmapdata; int bitmapbytecount; int bitmapbytesperrow; // image width, height. we'll use entire image. size_t pixelswide = cgimagegetwidth(inimage); size_t pixelshigh = cgimagegetheight(inimage); // declare number of bytes per row. each pixel in bitmap in // example represented 4 bytes; 8 bits each of red, green, blue, , // alpha. bitmapbytesperrow = (pixelswide * 4); bitmapbytecount = (bitmapbytesperrow * pixelshigh); // use generic rgb color space. //colorspace = cgcolorspacecreatewithname(kcgcolorspacegenericrgb); colorspace = cgcolorspacecreatedevicergb(); if (colorspace == null) { fprintf(stderr, "error allocating color space\n"); return null; } // allocate memory image data. destination in memory // drawing bitmap context rendered. bitmapdata = malloc( bitmapbytecount ); if (bitmapdata == null) { fprintf (stderr, "memory not allocated!"); cgcolorspacerelease( colorspace ); return null; } // create bitmap context. want pre-multiplied argb, 8-bits // per component. regardless of source image format // (cmyk, grayscale, , on) converted on format // specified here 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 , release colorspace before returning cgcolorspacerelease( colorspace ); return context; } - (uicolor*) getpixelcoloratlocation:(cgpoint)point { uicolor* color = nil; //cgimageref inimage = self.image.cgimage; cgimageref inimage = [appdelegate getinstance].capturedimage.cgimage; // create off screen bitmap context draw image into. format argb 4 bytes each pixel: alpa, red, green, blue cgcontextref cgctx = [self createargbbitmapcontextfromimage:inimage]; if (cgctx == null) { return nil; /* error */ } size_t w = cgimagegetwidth(inimage); size_t h = cgimagegetheight(inimage); cgrect rect = {{0,0},{w,h}}; // draw image bitmap context. once draw, memory // allocated context rendering contain // raw image data in specified color space. cgcontextdrawimage(cgctx, rect, inimage); // can pointer image data associated bitmap // context. unsigned char* data = cgbitmapcontextgetdata (cgctx); if (data != null) { //offset locates pixel in data x,y. //4 4 bytes of data per pixel, w width of 1 row of data. int offset = 4*((w*round(point.y))+round(point.x)); int alpha = data[offset]; int red = data[offset+1]; int green = data[offset+2]; int blue = data[offset+3]; nslog(@"offset: %i colors: rgb %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)]; } // when finished, release context cgcontextrelease(cgctx); // free image data memory context if (data) { free(data); } return color; } but none of these has been worked me. please me out work this. there i'm missing ?
i have 2 uiimageview in ui. 1 in contains image need pick color of pixel touched. , other uiimageview paint on image picked color.
please help. appreciated.
this 1 i've used, , looks simpler methods you've tried.
in custom view class, have this:
- (void)touchesbegan:(nsset *)touches withevent:(uievent *)event { uitouch *touch = [[event alltouches] anyobject]; cgpoint loc = [touch locationinview:self]; self.pickedcolor = [self colorofpoint:loc]; } colorofpoint method in category on uiview, code:
#import "uiview+colorofpoint.h" #import <quartzcore/quartzcore.h> @implementation uiview (colorofpoint) -(uicolor *) colorofpoint:(cgpoint)point { unsigned char pixel[4] = {0}; cgcolorspaceref colorspace = cgcolorspacecreatedevicergb(); cgcontextref context = cgbitmapcontextcreate(pixel, 1, 1, 8, 4, colorspace, (cgbitmapinfo)kcgimagealphapremultipliedlast); cgcontexttranslatectm(context, -point.x, -point.y); [self.layer renderincontext:context]; cgcontextrelease(context); cgcolorspacerelease(colorspace); uicolor *color = [uicolor colorwithred:pixel[0]/255.0 green:pixel[1]/255.0 blue:pixel[2]/255.0 alpha:pixel[3]/255.0]; return color; } don't forget import category custom view class , add quartzcore framework.
trivial note 2013: cast last argument (cgbitmapinfo) avoid implicit conversion warning: example here. hope helps.
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