Question

已经提出了类似的问题，但它们总是包含“使用UIImagePNGRepresentation或UIImageJPEGRepresentation”的答案，这对我不起作用。我需要将文件保存为位图。

根据我的理解，UIImage数据已经是位图。在这种情况下，我不应该创建一个位图。或者我呢？我找到了发布this question的人，但我不确定答案究竟是什么，因为我不清楚。我甚至创建了一个char指针数组，但我仍然不知道如何将其保存为位图。有没有人可以帮我理解如何将UIImage保存为位图？或者告诉我步骤，我会研究这些步骤。

谢谢。

编辑：

我发现this tutorial（带代码）用于将图像转换为位图，但返回的位图是无符号字符*。无论是我走在正确的道路上还是走错了方向。所以现在我要看看是否可以将unsigned char *写入.bmp文件。

Answer 1

下面是我为UIImage拼凑的类别，它允许我访问原始BGRA数据以及准备好使用适当的位图标题写入磁盘的数据。

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



# 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));

        if (rawData)
        {
            CGBitmapInfo bitmapInfo = kCGBitmapByteOrder32Little | 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 * 4) + 54;
    header.reserved1 = 0x0000;
    header.reserved2 = 0x0000;
    header.bitmapOffset = 0x00000036;
    header.headerSize = 0x00000028;
    header.width = width;
    header.height = height;
    header.colorPlanes = 0x0001;
    header.bitsPerPixel = 0x0020;
    header.compression = 0x00000000;
    header.bitmapSize = height * width * 4;
    header.horizontalResolution = 0x00000B13;
    header.verticalResolution = 0x00000B13;
    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

Objective C - 将UIImage保存为BMP文件

1 个答案: