通过本地PDF文件连接生产图片

#pragma mark - pdf转图片

// 通过本地PDF文件连接生产图片
+ (UIImage *)imageFromPDF:(NSURL *)url page:(NSInteger)page
{
    page = MAX(1, page);
    CFURLRef ref = (__bridge CFURLRef)url;
    CGPDFDocumentRef pdf = CGPDFDocumentCreateWithURL(ref);
    // 获取 PDF 页数
    NSInteger pageCount = CGPDFDocumentGetNumberOfPages(pdf);
    UIImage *amg;
    if (pageCount > 1) {
        NSMutableArray *imgs = @[].mutableCopy;
        for (int i = 1; i <= pageCount ; i++) {
            CGImageRef imageRef = createPDFPageToCGImage(i,pdf);
            UIImage *img = [UIImage imageWithCGImage:imageRef];
            [imgs addObject:img];
            CGImageRelease(imageRef);
        }
        amg = [self mergeImagesVertically:imgs];
    }
    else {
        CGImageRef imageRef = createPDFPageToCGImage(pageCount,pdf);
        amg = [UIImage imageWithCGImage:imageRef];
        CGImageRelease(imageRef);
    }
    CGPDFDocumentRelease(pdf);
    return amg;
}


CGContextRef CreateARGBBitmapContext(size_t pixelsWide, size_t pixelsHigh)
{
    CGContextRef context = NULL;
    CGColorSpaceRef colorSpace;
    void *bitmapData;
    size_t bitmapByteCount;
    size_t bitmapBytesPerRow;
    
    bitmapBytesPerRow  = (pixelsWide * 4);
    bitmapByteCount    = (bitmapBytesPerRow *pixelsHigh);
    
    // Use the generic RGB colorspace.
    colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
    if(colorSpace == NULL) {
        fprintf(stderr, "Error allocating colorspace\n");
        return NULL;
    }
    
    // Allocate memory for image data.This is the destination in memory
    // where any drawing to the bitmapcontext will be rendered.
    
    bitmapData = malloc( bitmapByteCount );
    
    if(bitmapData == NULL)
    {
        fprintf (stderr, "Memory notallocated!");
        CGColorSpaceRelease(colorSpace );
        return NULL;
    }
    
    context = CGBitmapContextCreate(bitmapData,
                                    
                                    pixelsWide,
                                    
                                    pixelsHigh,
                                    
                                    8,     // bits per component
                                    
                                    bitmapBytesPerRow,
                                    
                                    colorSpace,
                                    kCGImageAlphaPremultipliedFirst);
    
    if(context == NULL) {
        free (bitmapData);
        fprintf (stderr, "Context not created!");
    }
    CGColorSpaceRelease( colorSpace);
    return context;
}

CGImageRef createPDFPageToCGImage(size_t pageNumber, CGPDFDocumentRef document)
{
    CGPDFPageRef page;
    CGRect pageSize;
    CGContextRef outContext;
    CGImageRef ThePDFImage;
    page = CGPDFDocumentGetPage (document, pageNumber);
    if(page) {
        pageSize =CGPDFPageGetBoxRect(page,kCGPDFMediaBox);
        outContext= CreateARGBBitmapContext(pageSize.size.width, pageSize.size.height);
        
        if(outContext) {
            CGContextDrawPDFPage(outContext, page);
            ThePDFImage= CGBitmapContextCreateImage(outContext);
            CFRelease(outContext);
            return ThePDFImage;
        }
    }
    return NULL;
}

+ (UIImage *)mergeImagesVertically:(NSArray<UIImage *> *)imagesArray {
    CGFloat totalHeight = 0;
    CGFloat maxWidth = 0;

    // 计算总高度和最大宽度
    for (UIImage *image in imagesArray) {
        totalHeight += image.size.height;
        maxWidth = MAX(maxWidth, image.size.width);
    }

    // 开始创建图片上下文
    CGSize size = CGSizeMake(maxWidth, totalHeight);
    UIGraphicsBeginImageContext(size);

    CGFloat currentHeight = 0;
    for (UIImage *image in imagesArray) {
        [image drawAtPoint:CGPointMake((maxWidth - image.size.width) / 2, currentHeight)];
        currentHeight += image.size.height;
    }
    
    // 从上下文获取合并后的图片
    UIImage *finalImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return finalImage;
}