如何使用Objective C将.jpg图像转换为.bmp格式？

Anyone knows how to convert .jpg image to .bmp format in iphone using objective-C? And how i process(or RGB color) the each pixel of IPhone Device caputured image? Is there need to conversion of image type?

任何人都知道如何使用objective-C将.jpg图像转换为iPhone中的.bmp格式？以及我如何处理（或RGB颜色）iPhone设备捕获图像的每个像素？是否需要转换图像类型？

2 个解决方案

#1

You won't be able to easily get to a bmp representation on the iPhone. In Cocoa on the Mac, it is managed by the NSBitmapImageRep class and is pretty straight forward as outlined below.

您将无法轻松获得iPhone上的bmp表示。在Mac上的Cocoa中，它由NSBitmapImageRep类管理，并且非常简单，如下所述。

At a high level, you need to get the .jpg into an NSBitmapImageRep object and then let the frameworks handle the conversion for you:

在较高的层次上，您需要将.jpg转换为NSBitmapImageRep对象，然后让框架为您处理转换：

a. Convert the JPG image to an NSBitmapImageRep

一个。将JPG图像转换为NSBitmapImageRep

b. Use built in NSBitmapImageRep methods to save in desired formats.

湾使用内置的NSBitmapImageRep方法以所需格式保存。

NSBitmapImageRep *origImage = [self documentAsBitmapImageRep:[NSURL fileURLWithPath:pathToJpgImage]];
NSBitmapImageRep *bmpImage = [origImage representationUsingType:NSBMPFileType properties:nil];

- (NSBitmapImageRep*)documentAsBitmapImageRep:(NSURL*)urlOfJpg;
{

    CIImage *anImage = [CIImage imageWithContentsOfURL:urlOfJpg];
    CGRect outputExtent = [anImage extent];

    // Create a new NSBitmapImageRep.
    NSBitmapImageRep *theBitMapToBeSaved = [[NSBitmapImageRep alloc]  
                                            initWithBitmapDataPlanes:NULL pixelsWide:outputExtent.size.width  
                                            pixelsHigh:outputExtent.size.height  bitsPerSample:8 samplesPerPixel:4  
                                            hasAlpha:YES isPlanar:NO colorSpaceName:NSDeviceRGBColorSpace  
                                            bytesPerRow:0 bitsPerPixel:0];

    // Create an NSGraphicsContext that draws into the NSBitmapImageRep.  
    NSGraphicsContext *nsContext = [NSGraphicsContext graphicsContextWithBitmapImageRep:theBitMapToBeSaved];

    // Save the previous graphics context and state, and make our bitmap context current.
    [NSGraphicsContext saveGraphicsState];
    [NSGraphicsContext setCurrentContext: nsContext];
    CGPoint p = CGPointMake(0.0, 0.0);

    // Get a CIContext from the NSGraphicsContext, and use it to draw the CIImage into the NSBitmapImageRep.
    [[nsContext CIContext] drawImage:anImage atPoint:p fromRect:outputExtent];

    // Restore the previous graphics context and state.
    [NSGraphicsContext restoreGraphicsState];

    return [[theBitMapToBeSaved retain] autorelease];

}

On the iPhone, BMP is not directly supported by UIKit, so you would have to drop down into Quartz/Core Graphics and manage the transformation yourself.

在iPhone上，UIKit不直接支持BMP，因此您必须自己进入Quartz / Core Graphics并管理转换。

Pixel by pixel processing is much more involved. Again, you should get intimately familiar with the core graphics capabilities on the device if this is a hard requirement for you.

逐像素处理涉及更多。同样，如果这对您来说是一项艰难的要求，您应该非常熟悉设备上的核心图形功能。

#2

Load the JPG image into a UIImage, which it can handle natively.
将JPG图像加载到UIImage中，它可以本机处理。
Then you can grab the CGImageRef from the UIImage object.
然后你可以从UIImage对象中获取CGImageRef。
Create a new bitmap CG image context with the same properties of the image you already have, and provide your own data buffer to hold the bytes of the bitmap context.
创建一个新的位图CG图像上下文，其具有与您已有图像相同的属性，并提供您自己的数据缓冲区来保存位图上下文的字节。
Draw the original image into the new bitmap context: the bytes in your provided buffer are now the image's pixels.
将原始图像绘制到新的位图上下文中：提供的缓冲区中的字节现在是图像的像素。
Now you need to encode the actual BMP file, which isn't a functionality that exists in the UIKit or CoreGraphics (as far as I know) frameworks. Fortunately, it's an intentionally trivial format-- I've written quick and dirty encoders for BMP in an hour or less. Here's the spec: http://www.fileformat.info/format/bmp/egff.htm (Version 3 should be fine, unless you need to support alpha, but coming from JPEG you probably don't.)
现在你需要编码实际的BMP文件，这不是UIKit或CoreGraphics（据我所知）框架中存在的功能。幸运的是，这是一种有意无关紧要的格式 - 我在一小时或更短的时间内为BMP编写了快速而肮脏的编码器。这是规范：http：//www.fileformat.info/format/bmp/egff.htm（版本3应该没问题，除非你需要支持alpha，但是你可能不支持。）

Good luck.

祝你好运。

#1