IPhone image processing code snippets (continuously updated)

1. Image Scaling: Code -(Uiimage *) resizeimage :( uiimage *) image towidth :( nsinteger) width height :( nsinteger) height {// create a graphics context with the target size // on iOS 4 and later, use uigraphicsbeginimagecontextwittions to take the scale into consideration // on iOS prior to 4, fall back to use uigraphicsbeginimagecontext cgsize size = cgsizemake (width, height); If (null! = Optional) uigraphicsbeginimagecontextwitexceptions (size, no, 0); else uigraphicsbeginimagecontext (size); cgcontextref context = uigraphicsgetcurrentcontext (); // flip the context because uikit coordinate system is upside down to quartz coordinate system cgcontexttranslatectm (context, 0.0, height); cgcontextscalectm (context, 1.0,-1.0 ); // draw the original image to Context cgcontextsetblendmode (context, kcgblendmodecopy); cgcontextdrawimage (context, cgrectmake (0.0, 0.0, width, height), image. cgimage); // retrieve the uiimage from the current context uiimage * imageout = uigraphicsgetimagefromcurrentimagecontext (); uigraphicsendimagecontext (); Return imageout;} 2. uiview rotation: code-(void) rotateview :( uiview *) view toangle :( float) angle {[uiview beginanimations: Nil Co Ntext: Nil]; [view settransform: cgaffinetransformmakerotation (angle)]; [uiview commitanimations];} 3. color processing function: Code # pragma mark color convert-(uicolor *) str2color :( nsstring *) STR {sel blacksel = nsselectorfromstring (STR); // nsselectorfromstring (@ "blackcolor "); uicolor * tcolor = nil; If ([uicolor respondstoselector: blacksel]) tcolor = [uicolor performselector: blacksel]; return tcolor;}-(uicolor *) hex Str2color :( nsstring *) hexstr {nsstring * cstring = [[hexstr stringbytrimmingcharactersinset: [nscharacterset whitespaceandnewlinecharacterset] uppercasestring]; // string shoshould be 6 or 8 characters if ([cstring length] <6) return [uicolor blackcolor]; // strip 0x if it appears if ([cstring hasprefix: @ "0x"]) cstring = [cstring substringfromindex: 2]; If ([cstring length]! = 6) return [uicolor blackcolor]; // separate into R, G, B substrings nsange range; range. location = 0; range. length = 2; nsstring * rstring = [cstring substringwithrange: range]; range. location = 2; nsstring * gstring = [cstring substringwithrange: range]; range. location = 4; nsstring * bstring = [cstring substringwithrange: range]; // scan values unsigned int R, G, B; [[ns1_scannerwithstring: RST Ring] scanhexint: & R]; [[ns1_scannerwithstring: gstring] scanhexint: & G]; [ns1_scannerwithstring: bstring] scanhexint: & B]; return [uicolor colorwithred :( (float) r/255.0f) Green :( (float) g/255.0f) Blue :( (float) B/255.0f) ALPHA: 1.0f];} -(nsstring *) color2str :( uicolor *) color {cgcolorref c = color. cgcolor; const cgfloat * components = cgcolorgetcomponents (c); size_t numberofcomponents = Cgcolorgetnumberofcomponents (c); nsmutablestring * s = [[nsmutablestring alloc] init] autorelease]; [s appendstring: @ "{"]; for (size_t I = 0; I <numberofcomponents; ++ I) {if (I> 0) {[s appendstring: @ ","];} [s appendstring: [nsstring stringwithformat: @ "% d", (INT) (components [I] * 255)];} [s appendstring: @ "}"]; return s ;}- (nsstring *) color2str1 :( uicolor *) color {const cgfloat * components = Cgcolorgetcomponents (color. cgcolor); nsstring * colorasstring = [nsstring stringwithformat: @ "% 1f, % 1f, % 1f, % 1f", components [0] * 255, components [1] * 255, components [2] * 255, components [3];} 4. the angle corresponding to the intermediate point of the Three-Point coordinate, and determine whether the code is clockwise-(bool) chkclockwise :( cgpoint) a B :( cgpoint) B C :( cgpoint) c {double AX =. x-B. x; double ay =-. Y + B. y; double Cx = C. x-B. x; double Cy =-C. Y + B. y; nslog (@ "Result: % d", (CY * Ax) <= (Ay * CX); nslog (@ "(x1, Y1) = (% 1f, % 1f)", ax, ay); nslog (@ "(X2, Y2) = (% 1f, % 1f) \ r \ n ", CX, CY); Return (CY * Ax) <= (Ay * CX ));} 5. after the coordinates are rotated, the new coordinates are obtained: code-(cgpoint) getnewpoint: (cgpoint) Old rotate :( double) rotate {// The actual coordinates are converted to the origin coordinate old. X = (old. x-center.x); old. y = (center. y-old.y); // calculate the new coordinate after selection double X = old. x * Cos (rotate)-old. y * sin (rotate); Double Y = old. y * Cos (rotate) + Old. x * sin (rotate); // The origin coordinate is converted to the actual coordinate X = center. X + X; Y = center. y-y; return cgpointmake (x, y);} 6. capture the color of any point in uiview: code-(uicolor *) getpixelcoloratlocation :( cgpoint) point {uigraphicsbeginimagecontext (self. bounds. size); [self. layer renderincontext: uigraphicsgetcurrentcontext ()]; uiimage * viewimage = uigraphicsgetimagefromcurrentimagecontext (); uigraphicsendimagecontext (); cgimageref inimage = viewimage. cgimage; uicolor * color = nil; // create off SC Reen bitmap context to draw the image. format argb is 4 bytes for 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 the image to the bitmap context. once we draw, the memory // allo Cated 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. 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 a % 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 the context cgcontextrelease (cgctx ); // free image data memory for the context if (data) {free (data);} return color;}-(cgcontextref) createargbbitmapcontextfromimage :( cgimageref) inimage {cgcontextref context = NULL; cgcolorspaceref colorspace; void * bitmapdata; int bitmapbytecount; int bitmapbytesper Row; // 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 Space \ n"); 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 Located! "); 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 bitmapb Ytesperrow, colorspace, kcgimagealphapremultipliedfirst); If (context = NULL) {free (bitmapdata); fprintf (stderr, "context not created! ") ;}// Make sure and release colorspace before returning cgcolorspacerel.pdf (colorspace); Return context ;}7. On the iPhone Program // Import the header file # import <quartzcore/quartzcore. h> // set the entire self. create an image imageuigraphicsbeginimagecontext (self. view. bounds. size); [self. view. layer renderincontext: uigraphicsgetcurrentcontext ()]; uiimage * image = encrypt (); uigraphicsendimagecontext (); // Save the image to the image uiimagewritetosavedphotosalbum (image, self, nil, nil); 8. draw a dot image:-(uiimage *) createimage {cgsize size = [[uiscreen mainscreen] bounds]. size; cgrect rect = cgrectmake (size. width/2, size. height/2, 5, 5); uigraphicsbeginimagecontext (size); cgcontextref context = uigraphicsgetcurrentcontext (); unsigned int red, green, blue; // fill color. cgcontextsetrgbfillcolor (context, 0, 0.7, 0.7, 1.0); // your drawing code. cgcontextfillellipseinrect (context, rect); // get the image and return. uiimage * image = uigraphicsgetimagefromcurrentimagecontext (); uigraphicsendimagecontext (); Return image ;}