iOS常用小功能（获得屏幕图像、压缩图片、加边框、调整label的size）

摘要：获得屏幕图像,label的动态size,时间戳转化为时间,rgb转化成颜色,加边框,压缩图片,textfield的placeholder,图片做灰度处理

1.获得屏幕图像

- (uiimage *)imagefromview: (uiview *) theview
{
  uigraphicsbeginimagecontext(theview.frame.size);
  cgcontextref context = uigraphicsgetcurrentcontext();
  [theview.layer renderincontext:context];
  uiimage *theimage = uigraphicsgetimagefromcurrentimagecontext();
  uigraphicsendimagecontext();
  return theimage;
}

2.label的动态size

- (cgsize)labelautocalculaterectwith:(nsstring*)text fontsize:(cgfloat)fontsize maxsize:(cgsize)maxsize
{
  nsmutableparagraphstyle* paragraphstyle = [[nsmutableparagraphstyle alloc]init]; paragraphstyle.linebreakmode=nslinebreakbywordwrapping;
  nsdictionary* attributes =@{nsfontattributename:[uifont fontwithname:@"microsoftyahei" size:fontsize],nsparagraphstyleattributename:paragraphstyle.copy};
  cgsize labelsize = [text boundingrectwithsize:maxsize options:nsstringdrawinguseslinefragmentorigin|nsstringdrawingusesfontleading|nsstringdrawingtruncateslastvisibleline attributes:attributes context:nil].size;
  labelsize.height=ceil(labelsize.height);
  return labelsize;
}

3.时间戳转化为时间

-(nsstring*)timetrasformwithdate:(nsstring *)datestring
{
  nsdateformatter *formatter = [[nsdateformatter alloc]init];
  [formatter setdateformat:@"yy-mm-dd hh:mm"];
  [formatter settimezone:[nstimezone timezonewithname:@"asia/beijing"]];

  nsstring *date = [formatter stringfromdate:[nsdate datewithtimeintervalsince1970:datestring.integervalue]];
  //nslog(@"date1:%@",date);
  return date;
}

4.rgb转化成颜色

+ (uicolor *)colorfromhexrgb:(nsstring *)incolorstring
{
  uicolor *result = nil;
  unsigned int colorcode = 0;
  unsigned char redbyte, greenbyte, bluebyte;
  if (nil != incolorstring)
  {
    nsscanner *scanner = [nsscanner scannerwithstring:incolorstring];
    (void) [scanner scanhexint:&colorcode]; // ignore error
  }
  redbyte = (unsigned char) (colorcode >> 16);
  greenbyte = (unsigned char) (colorcode >> 8);
  bluebyte = (unsigned char) (colorcode); // masks off high bits
  result = [uicolor
       colorwithred: (float)redbyte / 0xff
       green: (float)greenbyte/ 0xff
       blue: (float)bluebyte / 0xff
       alpha:1.0];
  return result;
}

5.加边框

uirectcorner corners=uirectcornertopleft | uirectcornertopright;
  uibezierpath *maskpath = [uibezierpath bezierpathwithroundedrect:view.bounds        byroundingcorners:corners
 cornerradii:cgsizemake(4, 0)];
cashapelayer *masklayer = [cashapelayer layer];
masklayer.frame     = view.bounds;
masklayer.path     = maskpath.cgpath;
view.layer.mask     = masklayer;

6.//压缩图片

+ (uiimage*)imagewithimagesimple:(uiimage*)image scaledtosize:(cgsize)newsize
{
  //创建一个图形上下文形象
  uigraphicsbeginimagecontext(newsize);
  // 告诉旧图片画在这个新的环境,所需的
  // new size
  [image drawinrect:cgrectmake(0,0,newsize.width,newsize.height)];
  //获取上下文的新形象
  uiimage* newimage = uigraphicsgetimagefromcurrentimagecontext();
  // 结束上下文
  uigraphicsendimagecontext();
  return newimage;
}

7.textfield的placeholder

[textf setvalue:[uicolor whitecolor] forkeypath:@"_placeholderlabel.textcolor"];
[textf setvalue:[uifont boldsystemfontofsize:15] forkeypath:@"_placeholderlabel.font"];

8.布局

butleft. imageedgeinsets = uiedgeinsetsmake (7 , 5 , 7 , 25 );
butleft.contenthorizontalalignment = uicontrolcontenthorizontalalignmentcenter;

9.//调用此方法改变label最后2个字符的大小

- (void)label:(uilabel *)label behindtextsize:(nsinteger)integer
{
  nsmutableattributedstring *mutastring = [[nsmutableattributedstring alloc] initwithstring:label.text];

  [mutastring addattribute:nsfontattributename value:[uifont boldsystemfontofsize:16] range:nsmakerange(label.text.length-2, 2)];
  label.attributedtext = mutastring;
}

10.

- (void)changelabeltextcolor:(uilabel *)label
{
  nsmutableattributedstring *mutastring = [[nsmutableattributedstring alloc] initwithstring:label.text];
  [mutastring addattribute:nsforegroundcolorattributename value:[uicolor colorwithred:207/255.0 green:34/255.0 blue:42/255.0 alpha:1] range:nsmakerange(0, 5)];
  label.attributedtext = mutastring;
}

if ([tableview respondstoselector:@selector(setseparatorinset:)]) {
    [tableview setseparatorinset:uiedgeinsetszero];

  }
  if ([[uidevice currentdevice].systemversion floatvalue] >= 8.0) {
    if ([tableview respondstoselector:@selector(setlayoutmargins:)]) {
    [tableview setlayoutmargins:uiedgeinsetszero];
  }
  }
  // do any additional setup after loading the view.
}
- (void)tableview:(uitableview *)tableview willdisplaycell:(uitableviewcell *)cell forrowatindexpath:(nsindexpath *)indexpath
{
  if ([cell respondstoselector:@selector(setseparatorinset:)]) {
    [cell setseparatorinset:uiedgeinsetszero];
  }
  if ([[uidevice currentdevice].systemversion floatvalue] >= 8.0) {
    if ([cell respondstoselector:@selector(setlayoutmargins:)]) {
    [cell setlayoutmargins:uiedgeinsetszero];
  }
  }  
}

11.图片变灰度

-(uiimage *) grayscaleimage: (uiimage *) image
{
  cgsize size = image.size;
  cgrect rect = cgrectmake(0.0f, 0.0f, image.size.width,
               image.size.height);
  // create a mono/gray color space
  cgcolorspaceref colorspace = cgcolorspacecreatedevicegray();
  cgcontextref context = cgbitmapcontextcreate(nil, size.width,
                         size.height, 8, 0, colorspace, kcgimagealphanone);
  cgcolorspacerelease(colorspace);
  // draw the image into the grayscale context
  cgcontextdrawimage(context, rect, [image cgimage]);
  cgimageref grayscale = cgbitmapcontextcreateimage(context);
  cgcontextrelease(context);
  // recover the image
  uiimage *img = [uiimage imagewithcgimage:grayscale];
  cfrelease(grayscale);
  return img;
}

13.16进制转rgb

#define uicolorfromrgb(rgbvalue) [uicolor colorwithred:((float)((rgbvalue & 0xff0000) >> 16))/255.0 green:((float)((rgbvalue & 0xff00) >> 8))/255.0 blue:((float)(rgbvalue & 0xff))/255.0 alpha:1.0]

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