1. 图片缩放:
代码
- (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
-(CGPoint) getNewPoint: (CGPoint)old rotate:(double)rotate{
//实际坐标换算到原点坐标
old.x = (old.x-center.x);
old.y = (center.y-old.y);
//计算选转后新坐标
double x = old.x*cos(rotate)-old.y*sin(rotate);
double y = old.y*cos(rotate)+old.x*sin(rotate);
//原点坐标换算到实际坐标
x = center.x + x;
y = center.y - y;
return CGPointMake(x, y);
}
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;
}
图片处理代码片段
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原文地址：http://www.cnblogs.com/OIMM/p/4695637.html
