iOS开发笔记三

NSInterger to NSData

NSInterger to NSData,数字转化为Data,打印出来以十六进制形式展示

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- (NSData *)getDataWithInt:(NSInteger)interger {
Byte b1=interger & 0xff;
Byte b2=(interger>>8) & 0xff;
Byte b3=(interger>>16) & 0xff;
Byte b4=(interger>>24) & 0xff;
if (interger <= 255) {
Byte byte[] = {b1};
return [NSData dataWithBytes:byte length:sizeof(byte)];
} else if (interger <= 65535) {
Byte byte[] = {b2,b1};
return [NSData dataWithBytes:byte length:sizeof(byte)];
} else if (interger <= 16777215) {
Byte byte[] = {b3,b2,b1};
return [NSData dataWithBytes:byte length:sizeof(byte)];
} else {
Byte byte[] = {b4,b3,b2,b1};
return [NSData dataWithBytes:byte length:sizeof(byte)];
}
}

SHA1加密

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- (NSString *)SHA1Encrypt:(NSString *)string{
const char *cstr = [string UTF8String];
NSData *data = [NSData dataWithBytes:cstr length:string.length];
uint8_t digest[CC_SHA1_DIGEST_LENGTH];
CC_SHA1(data.bytes, (CC_LONG)data.length, digest);
NSMutableString *output = [NSMutableString stringWithCapacity:CC_SHA1_DIGEST_LENGTH *2];
for (int i = 0; i<CC_SHA1_DIGEST_LENGTH; i++) {
[output appendFormat:@"%02x",digest[i]];
}
return output;
}

iPhone屏幕单位

ios开发中设置的size为pt,pt是绝对长度,等于1/72英寸,等于1/72*25.4毫米。

px是像素,像素点的密度代表着屏幕清晰度。这就是开发中@1x、@2x、@3x的区别。

iPhone 3GS是@1x像素级,分辨率为480px 320px,iPhone4是@2x像素级,分辨率为960px 640px。这两者尺寸是一样的,所以pt是一样的,在同样大的范围内,iPhone 4的像素点比iPhone 3GS的多一倍。

QR码的一些知识点

QR码有40个版本,版本1是21 x 21个小方块组成,版本2是25 x 25个小方块,每增加1版本,二维码长宽各增加4个方块。所以最高版本40,方块数为177 177。计算公式是:(V-1) 4 + 21

使用CIFilter生成QR码

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//生码Objective-C
- (UIImage *)markCode:(NSString *)code {
CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
[filter setDefaults];
NSData *data = [code dataUsingEncoding:NSUTF8StringEncoding];
[filter setValue:data forKey:@"inputMessage"];
[filter setValue:@"L" forKey:@"inputCorrectionLevel"]; //二维码的纠错级别 L < H < Q < M
CIColor *color1 = [CIColor colorWithCGColor:[UIColor blackColor].CGColor];//二维码颜色
CIColor *color2 = [CIColor colorWithCGColor:[UIColor whiteColor].CGColor];//背景色
NSDictionary *parameters = [NSDictionary dictionaryWithObjectsAndKeys: filter.outputImage ,@"inputImage", color1,@"inputColor0", color2,@"inputColor1",nil];
CIFilter *newFilter = [CIFilter filterWithName:@"CIFalseColor" withInputParameters:parameters];
CIImage *outPutImage = [newFilter outputImage];
int version = (int)((outPutImage.extent.size.width - 21) / 4.0 + 1); //获取该二维码的版本号
return [self createNonInterpolatedUIImageFormCIImage:outPutImage withSize:600];
}
//让二维码变的清楚
- (UIImage *)createNonInterpolatedUIImageFormCIImage:(CIImage *)image withSize:(CGFloat) size {
CGRect extent = CGRectIntegral(image.extent);
CGFloat scale = MIN(size/CGRectGetWidth(extent), size/CGRectGetHeight(extent));
size_t width = CGRectGetWidth(extent) * scale;
size_t height = CGRectGetHeight(extent) * scale;
CGColorSpaceRef cs = CGColorSpaceCreateDeviceRGB();
CGContextRef bitmapRef = CGBitmapContextCreate(nil, width, height, 8, 0, cs, (CGBitmapInfo)kCGImageAlphaPremultipliedLast);
CIContext *context = [CIContext contextWithOptions:nil];
CGImageRef bitmapImage = [context createCGImage:image fromRect:extent];
CGContextSetInterpolationQuality(bitmapRef, kCGInterpolationNone);
CGContextScaleCTM(bitmapRef, scale, scale);
CGContextDrawImage(bitmapRef, extent, bitmapImage);
CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);
CGContextRelease(bitmapRef); CGImageRelease(bitmapImage);
UIImage *outputImage = [UIImage imageWithCGImage:scaledImage];
return outputImage;
}
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