如何使用目標c將JPEG文件轉換爲BITMAP？

Question

我想使用Objective C將jpeg文件轉換爲位圖。我們必須將其轉換爲png，但目標c中沒有具體方法將jpeg轉換爲位圖。

Answer 1

首先從jpeg圖像創建BGR數組。創建位圖圖像標題（所有bmp圖像具有相同的標題）。將字頭附加到字節數組，然後像B字節一樣添加BGR數組，然後像明智那樣添加G字節和r字節。然後最後將字節數組轉換爲NSDATA。您將獲得BMP圖像的數據。此代碼適用於具有512 X 512像素的圖像，BMP圖像會轉換爲24位bmp圖像。在代碼SIDE = 512。 imgpath將像「users/admin」一樣，destimgpath將會像「users/admin/bmpfolder」一樣。文件名將如1.jpg

-(void) convertJpegToBmp: (NSString *)imgDirPath :(NSString *)destImgPath :(NSString *)fileName 
{ 
NSString *jpegimagepath = [imgDirPath stringByAppendingPathComponent:fileName]; 
NSString *fileNameWithoutExtension=[[fileName lastPathComponent] stringByDeletingPathExtension]; 
NSString *bmpFileName=[fileNameWithoutExtension stringByAppendingString:@".bmp"]; 
NSString *bmpfilepath=[destImgPath stringByAppendingPathComponent:bmpFileName]; 
int totalbytesinbitmap=(int) (SIDE * SIDE * 3)+54; 
Byte bytes[totalbytesinbitmap]; 
[self writeBitmapHeader:bytes]; 
UIImage *sourceImage1=[UIImage imageWithContentsOfFile:jpegimagepath]; 
if(sourceImage1==nil) 
    return; 
CGImageRef sourceImage = sourceImage1.CGImage; 
CFDataRef theData; 
theData = CGDataProviderCopyData(CGImageGetDataProvider(sourceImage)); 
UInt8 *pixelDataS = (UInt8 *) CFDataGetBytePtr(theData); 
int dataLength = (int)CFDataGetLength(theData); 
int k=54; 
int row=(int) SIDE -1 ; 
int col=0; 
int totalbytesinrow=(int) SIDE * 3; 
for(int i=0;i<dataLength;){ 
    int red=pixelDataS[i++]; 
    int green=pixelDataS[i++]; 
    int blue=pixelDataS[i++]; 
     i++; 
    if(col==totalbytesinrow){ 
     col=0; 
     row--; 
    } 
    int location=(row * totalbytesinrow)+col+54; 
    bytes[location]=blue; 
    col++; 
    k++; 
    bytes[location+1]=green; 
    col++; 
    k++; 
    bytes[location+2]=red; 
    col++; 
    k++; 
} 
NSData *TxData = [NSData dataWithBytesNoCopy:bytes length:totalbytesinbitmap freeWhenDone:NO]; 
[TxData writeToFile:bmpfilepath atomically:YES]; 
} 

-(void) writeBitmapHeader:(Byte *) pixelData{ 
int BITMAPHEADER_SIZE= 14; 
int BITMAPINFOHEADER_SIZE=40; 
Byte bfType[]={ (Byte)'B', (Byte)'M'}; 
int bfSize=0; 
int bfReserved1=0; 
int bfReserved2=0; 
int bfOffBits=BITMAPHEADER_SIZE+BITMAPINFOHEADER_SIZE; 
int biSize = BITMAPINFOHEADER_SIZE; 
int biWidth = 0; 
int biHeight = 0; 
int biPlanes = 1; 
int biBitCount = 24; 
int biCompression = 0; 
int biSizeImage = 0x030000; 
int biXPelsPerMeter = 0x0; 
int biYPelsPerMeter = 0x0; 
int biClrUsed = 0; 
int biClrImportant = 0; 
int parWidth=(int)SIDE; 
int parHeight =(int)SIDE; 
int pad= (4 -((parWidth * 3) %4)) * parHeight; 
if((4 -((parWidth * 3) %4))==4) 
{ 
    pad=0; 
} 
biSizeImage= ((parWidth * parHeight) *3)+pad; 
bfSize= biSizeImage + BITMAPHEADER_SIZE+BITMAPINFOHEADER_SIZE; 
biWidth=parWidth; 
biHeight=parHeight; 
int count=0; 
pixelData[count++]=bfType[0]; 
pixelData[count++]=bfType[1]; 
count=[self intToDWord:bfSize :pixelData :count]; 
count=[self intToWord:bfReserved1 :pixelData :count]; 
count=[self intToWord:bfReserved2 :pixelData :count]; 
count=[self intToDWord:bfOffBits :pixelData :count]; 
count=[self intToDWord:biSize :pixelData :count]; 
count=[self intToDWord:biWidth :pixelData :count]; 
count=[self intToDWord:biHeight :pixelData :count]; 
count=[self intToWord:biPlanes :pixelData :count]; 
count=[self intToWord:biBitCount :pixelData :count]; 
count=[self intToDWord:biCompression :pixelData :count]; 
count=[self intToDWord:biSizeImage :pixelData :count]; 
count=[self intToDWord:biXPelsPerMeter :pixelData :count]; 
count=[self intToDWord:biYPelsPerMeter :pixelData :count]; 
count=[self intToDWord:biClrUsed :pixelData :count]; 
count=[self intToDWord:biClrImportant :pixelData :count]; 

} 

-(int) intToWord :(int) parValue :(Byte *) pixelData :(int) count{ 
pixelData[count++]= (Byte) (parValue & 0x00ff); 
pixelData[count++]= (Byte) ((parValue >> 8) & 0x00ff); 
return count; 
} 

-(int) intToDWord :(int) parValue :(Byte *) pixelData :(int) count{ 
    pixelData[count++]= (Byte) (parValue & 0x000000FF); 
    pixelData[count++]= (Byte) ((parValue >> 8) & 0x000000FF); 
    pixelData[count++]= (Byte) ((parValue >> 16) & 0x000000FF); 
    pixelData[count++]= (Byte) ((parValue >> 24) & 0x000000FF); 
    return count; 
}