如何在图像中放置黑色矩形

Question

我有png文件的路径（图片）。我想在同一个文件夹中创建新图像，此图像的中心将是尺寸为300x100的黑色矩形。然后我需要获得新创建的Image的路径。

有人可以帮我解决这个问题吗？

我正在玩这个代码：

- (void) grayscale:(UIImage*) image {
    CGContextRef ctx;
    CGImageRef imageRef = [image CGImage];
    NSUInteger width = CGImageGetWidth(imageRef);
    NSUInteger height = CGImageGetHeight(imageRef);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    unsigned char *rawData = malloc(height * width * 4);
    NSUInteger bytesPerPixel = 4;
    NSUInteger bytesPerRow = bytesPerPixel * width;
    NSUInteger bitsPerComponent = 8;
    CGContextRef context = CGBitmapContextCreate(rawData, width, height,
                                                 bitsPerComponent, bytesPerRow, colorSpace,
                                                 kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    CGColorSpaceRelease(colorSpace);

    CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
    CGContextRelease(context);

    // Now your rawData contains the image data in the RGBA8888 pixel format.
    NSUInteger byteIndex = (bytesPerRow * 0) + 0 * bytesPerPixel;
    for (int ii = 0 ; ii < width * height ; ++ii)
    {
        // Get color values to construct a UIColor
        CGFloat red   = (rawData[byteIndex]     * 1.0) / 255.0;
        CGFloat green = (rawData[byteIndex + 1] * 1.0) / 255.0;
        CGFloat blue  = (rawData[byteIndex + 2] * 1.0) / 255.0;
        CGFloat alpha = (rawData[byteIndex + 3] * 1.0) / 255.0;

        rawData[byteIndex] = (char) (red);
        rawData[byteIndex+1] = (char) (green);
        rawData[byteIndex+2] = (char) (blue);

        byteIndex += 4;
    }

    ctx = CGBitmapContextCreate(rawData,
                                CGImageGetWidth( imageRef ),
                                CGImageGetHeight( imageRef ),
                                8,
                                CGImageGetBytesPerRow( imageRef ),
                                CGImageGetColorSpace( imageRef ),
                                kCGImageAlphaPremultipliedLast );

    imageRef = CGBitmapContextCreateImage (ctx);
    UIImage* rawImage = [UIImage imageWithCGImage:imageRef];

    CGContextRelease(ctx);

    self.workingImage = rawImage;
    [self.imageView setImage:self.workingImage];

    free(rawData);

}

但我没有成功。

Answer 1

是的，您可以在其上绘制另一个黑色图层。请参阅下面我的代码，它将满足您的要求：

注意：请在您的代码中添加“testImage.png”图片，然后执行以下代码。

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController
@synthesize strTemp3;

- (void)viewDidLoad {
    [super viewDidLoad];

    [self testImageWrite];
    [self addNewImageFromPath];    
}

- (UIImage *)imageToDraw
{
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(300, 100), NO, [UIScreen mainScreen].scale);
    UIImage *natureImage = [UIImage imageNamed:@"testImage"];
    [natureImage drawInRect:CGRectMake(0, 0, 300, 100)];

    CGContextRef context = UIGraphicsGetCurrentContext();
    CGRect rectangle = CGRectMake(75, 25, 150, 50);
    CGContextSetRGBFillColor(context, 0.0, 0.0, 0.0, 1.0);
    CGContextSetRGBStrokeColor(context, 0.0, 0.0, 0.0, 1.0);
    CGContextFillRect(context, rectangle);

    UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return resultingImage;
}

- (NSString *)filePath
{
    NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask,YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    return [documentsDirectory stringByAppendingPathComponent:@"Image.png"];
}

- (void)testImageWrite
{
    NSData *imageData = UIImagePNGRepresentation([self imageToDraw]);
    NSError *writeError = nil;
    BOOL success = [imageData writeToFile:[self filePath] options:0 error:&writeError];
    if (!success || writeError != nil)
    {
        NSLog(@"Error Writing: %@",writeError.description);
    }
}

-(void)addNewImageFromPath{
    UIImageView *imgView = [[UIImageView alloc] initWithFrame:CGRectMake(10, 10, 300, 100)];
    imgView.image = [UIImage imageWithContentsOfFile:[self filePath]];
    [self.view addSubview:imgView];
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];    
}

<强>输出：

实际图片：

新图片