BMP格式

#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface UIImage (BitmapData)
- (NSData *)bitmapData;
- (NSData *)bitmapFileHeaderData;
- (NSData *)bitmapDataWithFileHeader;
@end

NS_ASSUME_NONNULL_END

#import "UIImage+BitmapData.h"


# pragma pack(push, 1)
typedef struct s_bitmap_header
{
    // Bitmap file header
    UInt16 fileType;
    UInt32 fileSize;
    UInt16 reserved1;
    UInt16 reserved2;
    UInt32 bitmapOffset;
    
    // DIB Header
    UInt32 headerSize;
    UInt32 width;
    UInt32 height;
    UInt16 colorPlanes;
    UInt16 bitsPerPixel;
    UInt32 compression;
    UInt32 bitmapSize;
    UInt32 horizontalResolution;
    UInt32 verticalResolution;
    UInt32 colorsUsed;
    UInt32 colorsImportant;
} t_bitmap_header;
#pragma pack(pop)

@implementation UIImage (BitmapData)

- (NSData *)bitmapData
{
    NSData          *bitmapData = nil;
    CGImageRef      image = self.CGImage;
    CGContextRef    context = NULL;
    CGColorSpaceRef colorSpace;
    UInt8           *rawData;
    
    size_t bitsPerPixel = 32;
    size_t bitsPerComponent = 8;
    size_t bytesPerPixel = bitsPerPixel / bitsPerComponent;
    
    size_t width = CGImageGetWidth(image);
    size_t height = CGImageGetHeight(image);
    
    size_t bytesPerRow = width * bytesPerPixel;
    size_t bufferLength = bytesPerRow * height;
    
    colorSpace = CGColorSpaceCreateDeviceRGB();
    
    if (colorSpace)
    {
        // Allocate memory for raw image data
        rawData = (UInt8 *)calloc(bufferLength, sizeof(UInt8));
        NSLog(@"---%lu", sizeof(rawData));
        if (rawData)
        {
            CGBitmapInfo bitmapInfo = kCGImageByteOrder32Little | kCGImageAlphaPremultipliedFirst;
            context = CGBitmapContextCreate(rawData,
                                            width,
                                            height,
                                            bitsPerComponent,
                                            bytesPerRow,
                                            colorSpace,
                                            bitmapInfo);
            
            if (context)
            {
                CGRect rect = CGRectMake(0, 0, width, height);
                
                CGContextTranslateCTM(context, 0, height);
                CGContextScaleCTM(context, 1.0, -1.0);
                CGContextDrawImage(context, rect, image);
                
                bitmapData = [NSData dataWithBytes:rawData length:bufferLength];
                
                CGContextRelease(context);
            }
            
            free(rawData);
        }
        
        CGColorSpaceRelease(colorSpace);
    }
    
    return bitmapData;
}

- (NSData *)bitmapFileHeaderData
{
    CGImageRef image = self.CGImage;
    UInt32     width = (UInt32)CGImageGetWidth(image);
    UInt32     height = (UInt32)CGImageGetHeight(image);
    
    t_bitmap_header header;
    header.fileType = 0x4D42;
    header.fileSize = (height * width * 3) + 54;
    header.reserved1 = 0x0000;
    header.reserved2 = 0x0000;
    header.bitmapOffset = 0x00000036;
    header.headerSize = 0x00000028;
    header.width = width;
    header.height = height;
    header.colorPlanes = 0x0001;
    header.bitsPerPixel = 0x0018;
    header.compression = 0x00000000;
    header.bitmapSize = width * height * 3;
    header.horizontalResolution = 0x00000000;
    header.verticalResolution = 0x00000000;
    header.colorsUsed = 0x00000000;
    header.colorsImportant = 0x00000000;
    
    return [NSData dataWithBytes:&header length:sizeof(t_bitmap_header)];
}

- (NSData *)bitmapDataWithFileHeader
{
    NSMutableData *data = [NSMutableData dataWithData:[self bitmapFileHeaderData]];
    [data appendData:[self bitmapData]];
    
    return [NSData dataWithData:data];
}


@end

備注

bitmapFileHeaderData可以跟自己實際需求改寫