如何在 Objective-C 中将字节数组转换为图像

Question

就是这样
我有一个指向 BMP 图像数据的无符号字符指针
在我用指针循环后，我实现了一个包含 int 值 0 - 255 的字节数组

我想要的是将数组中的这个值转换为 BMP 图像 在 UIImage 中显示。

**图片为灰度图

Answer 1

我会想象这样的事情。未经测试，所以准备好调整:)

UIImage *yourImage = [UIImage imageWithData: [NSData dataWithBytes: yourCharPointer length : sizeof(yourCharPointer)]];

Answer 2

这个代码sn-p来自这个blog，我建议你看看那里和project site in Github

另请注意，此类方法适用于 RGB8 图像，因此您需要在 bitsPerPixel（灰度应为 8）、bytesPerRow（1 * 宽度）、bufferLength（删除 * 4）并使用 CGColorCreateGenericGray 创建 colorSpaceRef。

我还注意到，使用 CGColorCreateGenericGray 创建色彩空间假设您的数组具有 alpha 信息。所以也许你应该为每个像素添加一个 alpha 字节以使其正常工作。

+ (UIImage *) convertBitmapRGBA8ToUIImage:(unsigned char *) buffer 
            withWidth:(int) width
           withHeight:(int) height {


    size_t bufferLength = width * height * 4;
    CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer, bufferLength, NULL);
    size_t bitsPerComponent = 8;
    size_t bitsPerPixel = 32;
    size_t bytesPerRow = 4 * width;

    CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
    if(colorSpaceRef == NULL) {
        NSLog(@"Error allocating color space");
        CGDataProviderRelease(provider);
        return nil;
    }

    CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedLast;
    CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;

    CGImageRef iref = CGImageCreate(width, 
                height, 
                bitsPerComponent, 
                bitsPerPixel, 
                bytesPerRow, 
                colorSpaceRef, 
                bitmapInfo, 
                provider,   // data provider
                NULL,       // decode
                YES,            // should interpolate
                renderingIntent);

    uint32_t* pixels = (uint32_t*)malloc(bufferLength);

    if(pixels == NULL) {
        NSLog(@"Error: Memory not allocated for bitmap");
        CGDataProviderRelease(provider);
        CGColorSpaceRelease(colorSpaceRef);
        CGImageRelease(iref);       
        return nil;
    }

    CGContextRef context = CGBitmapContextCreate(pixels, 
                 width, 
                 height, 
                 bitsPerComponent, 
                 bytesPerRow, 
                 colorSpaceRef, 
                 bitmapInfo); 

    if(context == NULL) {
        NSLog(@"Error context not created");
        free(pixels);
    }

    UIImage *image = nil;
    if(context) {

        CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, width, height), iref);

        CGImageRef imageRef = CGBitmapContextCreateImage(context);

        // Support both iPad 3.2 and iPhone 4 Retina displays with the correct scale
        if([UIImage respondsToSelector:@selector(imageWithCGImage:scale:orientation:)]) {
            float scale = [[UIScreen mainScreen] scale];
            image = [UIImage imageWithCGImage:imageRef scale:scale orientation:UIImageOrientationUp];
        } else {
            image = [UIImage imageWithCGImage:imageRef];
        }

        CGImageRelease(imageRef);   
        CGContextRelease(context);  
    }

    CGColorSpaceRelease(colorSpaceRef);
    CGImageRelease(iref);
    CGDataProviderRelease(provider);

    if(pixels) {
        free(pixels);
    }   
    return image;
}

Answer 3

由于接受的答案太长，我写了另一个解决方案：

- (UIImage*) imageFromArray:(const char*)pixelArray width:(int)width height:(int)height {

    int imageSizeInPixels = width * height;
    int bytesPerPixel = 2; // 1 byte for brightness, 1 byte for alpha
    unsigned char *pixels = (unsigned char *)malloc(imageSizeInPixels * bytesPerPixel);
    memset(pixels, 255, imageSizeInPixels * bytesPerPixel); // setting alpha values to 255
    for (int i = 0; i < imageSizeInPixels; i++) {
        pixels[i * 2] = pixelArray[i]; // writing array of bytes as image brightnesses
    }

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
    CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, pixels, imageSizeInPixels * bytesPerPixel, NULL);
    CGImageRef cgImage = CGImageCreate(width, height, 8, 8 * bytesPerPixel, width * bytesPerPixel, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big, provider, NULL, false, kCGRenderingIntentDefault);
    UIImage *image = [UIImage imageWithCGImage:cgImage];

    return image;
}