iOS图像处理片段

- (UIImage*)resizeImage:(UIImage*)image toWidth:(NSInteger)width height:(NSInteger)height

{

// Create a graphics context with the target size

// On iOS 4 and later, use UIGraphicsBeginImageContextWithOptions to take the scale into consideration

// On iOS prior to 4, fall back to use UIGraphicsBeginImageContext

CGSize size = CGSizeMake(width, height);

if (NULL != UIGraphicsBeginImageContextWithOptions)

UIGraphicsBeginImageContextWithOptions(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 the 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旋转：


代码

- (void)rotateView:(UIView *)view toAngle:(float)angle

{

[UIView beginAnimations:nil context:nil];

[view setTransform:CGAffineTransformMakeRotation(angle)];

[UIView commitAnimations];

}

3. 颜色处理函数：


代码

#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 *) hexStr2Color:(NSString *)hexStr {

NSString *cString = [[hexStr stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] uppercaseString];

// String should 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

NSRange 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;

[[NSScanner scannerWithString:rString] scanHexInt:&r];

[[NSScanner scannerWithString:gString] scanHexInt:&g];

[[NSScanner 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. 三点坐标中间点对应的角度，以及判断是否顺时针


代码

-(BOOL) chkClockWise:(CGPoint)a B:(CGPoint)b C:(CGPoint)c {

double ax = a.x - b.x;

double ay = - a.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\r\n",cx, cy);

return ((cy*ax)<=(ay*cx));

}

5. 点坐标旋转后弧度后获取新的坐标：


代码

6. 抓取UIView上任意点的颜色：


代码

- (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 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; /* 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

// 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.

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 %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 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 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 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 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;

}

7. 在iphone程序中实现截屏的一种方法：

//导入头文件

#import <QuartzCore/QuartzCore.h>

//将整个self.view大小的图层内容创建一张图片image

UIGraphicsBeginImageContext(self.view.bounds.size);

[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];

UIImage *image= UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

//然后将该图片保存到图片图

UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);

8. 画圆点图片：

-(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;

}