我有一个带有ImageView的Profile视图，用户可以在其中更改图片。我正在拯救我的老人和我新图像来比较它们。我想知道它们是否相同，所以如果它们我不需要将新的推送到我的服务器。
我尝试了这个，但它确实不起作用：
+ (NSData*)returnImageAsData:(UIImage *)anImage {
// Get an NSData representation of our images. We use JPEG for the larger image
// for better compression and PNG for the thumbnail to keep the corner radius transparency
float i_width = 400.0f;
float oldWidth = anImage.size.width;
float scaleFactor = i_width / oldWidth;
float newHeight = anImage.size.height * scaleFactor;
float newWidth = oldWidth * scaleFactor;
UIGraphicsBeginImageContext(CGSizeMake(newWidth, newHeight));
[anImage drawInRect:CGRectMake(0, 0, newWidth, newHeight)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
NSData *imageData = UIImageJPEGRepresentation(newImage, 0.5f);
return imageData;
}
+ (BOOL)image:(UIImage *)image1 isEqualTo:(UIImage *)image2
{
NSData *data1 = [self returnImageAsData:image1];
NSData *data2 = [self returnImageAsData:image2];
return [data1 isEqual:data2];
}
知道如何检查两张图片是否相同？
最终结果：
+ (NSData*)returnImageAsData:(UIImage *)anImage {
// Get an NSData representation of our images. We use JPEG for the larger image
// for better compression and PNG for the thumbnail to keep the corner radius transparency
// float i_width = 400.0f;
// float oldWidth = anImage.size.width;
// float scaleFactor = i_width / oldWidth;
//
// float newHeight = anImage.size.height * scaleFactor;
// float newWidth = oldWidth * scaleFactor;
//
// UIGraphicsBeginImageContext(CGSizeMake(newWidth, newHeight));
// [anImage drawInRect:CGRectMake(0, 0, newWidth, newHeight)];
// UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
// UIGraphicsEndImageContext();
NSData *imageData = UIImageJPEGRepresentation(anImage, 0.5f);
return imageData;
}
+ (BOOL)image:(UIImage *)image1 isEqualTo:(UIImage *)image2
{
CGSize size1 = image1.size;
CGSize size2 = image2.size;
if (CGSizeEqualToSize(size1, size2)) {
return YES;
}
NSData *data1 = UIImagePNGRepresentation(image1);
NSData *data2 = UIImagePNGRepresentation(image2);
return [data1 isEqual:data2];
}
答案 0 :(得分：1)
如果你想看看2张图像是否像素相同，那应该很容易。
将图像保存为JPEG可能会导致问题，因为JPEG格式是有损格式。
正如其他人所建议的那样，首先要确保两个图像的高度和宽度相匹配。如果没有，停止。图像不同。
如果匹配，请使用UIImagePNGRepresentation（）之类的函数将图像转换为无损数据格式。然后在你回来的NSData对象上使用isEqual。
如果你想检查图像是否相同（比如同一场景的2张照片），你手上的问题会更加严重。您可能不得不求助于像OpenCV这样的软件包来比较图像。
编辑：我不知道UIImage是否有一个isEqual的自定义实现，你可以使用它来比较两个图像。我先试试。查看文档，UIImage也符合NSCoding，因此您可以使用archivedDataWithRootObject将图像转换为数据。这可能比编码它们的PNG更快。
最后，你可以得到一个指向图像的底层CGImage对象的指针，获取它们的数据提供者，并以这种方式比较它们的字节流。
答案 1 :(得分：1)
检查相同尺寸，然后检查哈希值......
答案 2 :(得分：1)
以下一步一步： 第一步是缩小尺寸。将大小减小到8x8，总共64像素。这一步的作用是去除图片的细节，只保留结构，光线等基本信息，放弃不同大小，图片比例的差异。
-(UIImage * ) OriginImage:(UIImage **)image scaleToSize:(CGSize)size
{
UIGraphicsBeginImageContext(size);
[image drawInRect:CGRectMake(0, 0, size.width, size.height)];
UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return scaledImage;
}
第2步，简化颜色。将图片缩小到64灰度。也就是说，所有像素总共有64种颜色。
-(UIImage*)getGrayImage:(UIImage*)sourceImage
{
int width = sourceImage.size.width;
int height = sourceImage.size.height;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
CGContextRef context = CGBitmapContextCreate (nil,width,height,8,0,colorSpace,kCGImageAlphaNone);
CGColorSpaceRelease(colorSpace);
if (context == NULL) {
return nil;
}
CGContextDrawImage(context,CGRectMake(0, 0, width, height), sourceImage.CGImage);
UIImage *grayImage = [UIImage imageWithCGImage:CGBitmapContextCreateImage(context)];
CGContextRelease(context);
return grayImage;
}
步骤3是计算平均值。计算所有64个像素的灰度。
-(unsigned char*) grayscalePixels:(UIImage *) image
{
// The amount of bits per pixel, in this case we are doing grayscale so 1 byte = 8 bits
#define BITS_PER_PIXEL 8
// The amount of bits per component, in this it is the same as the bitsPerPixel because only 1 byte represents a pixel
#define BITS_PER_COMPONENT (BITS_PER_PIXEL)
// The amount of bytes per pixel, not really sure why it asks for this as well but it's basically the bitsPerPixel divided by the bits per component (making 1 in this case)
#define BYTES_PER_PIXEL (BITS_PER_PIXEL/BITS_PER_COMPONENT)
// Define the colour space (in this case it's gray)
CGColorSpaceRef colourSpace = CGColorSpaceCreateDeviceGray();
// Find out the number of bytes per row (it's just the width times the number of bytes per pixel)
size_t bytesPerRow = image.size.width * BYTES_PER_PIXEL;
// Allocate the appropriate amount of memory to hold the bitmap context
unsigned char* bitmapData = (unsigned char*) malloc(bytesPerRow*image.size.height);
// Create the bitmap context, we set the alpha to none here to tell the bitmap we don't care about alpha values
CGContextRef context = CGBitmapContextCreate(bitmapData,image.size.width,image.size.height,BITS_PER_COMPONENT,bytesPerRow,colourSpace,kCGImageAlphaNone);
// We are done with the colour space now so no point in keeping it around
CGColorSpaceRelease(colourSpace);
// Create a CGRect to define the amount of pixels we want
CGRect rect = CGRectMake(0.0,0.0,image.size.width,image.size.height);
// Draw the bitmap context using the rectangle we just created as a bounds and the Core Graphics Image as the image source
CGContextDrawImage(context,rect,image.CGImage);
// Obtain the pixel data from the bitmap context
unsigned char* pixelData = (unsigned char*)CGBitmapContextGetData(context);
// Release the bitmap context because we are done using it
CGContextRelease(context);
return pixelData;
#undef BITS_PER_PIXEL
#undef BITS_PER_COMPONENT
}
返回0101字符串
-(NSString *) myHash:(UIImage *) img
{
unsigned char* pixelData = [self grayscalePixels:img];
int total = 0;
int ave = 0;
for (int i = 0; i < img.size.height; i++) {
for (int j = 0; j < img.size.width; j++) {
total += (int)pixelData[(i*((int)img.size.width))+j];
}
}
ave = total/64;
NSMutableString *result = [[NSMutableString alloc] init];
for (int i = 0; i < img.size.height; i++) {
for (int j = 0; j < img.size.width; j++) {
int a = (int)pixelData[(i*((int)img.size.width))+j];
if(a >= ave)
{
[result appendString:@"1"];
}
else
{
[result appendString:@"0"];
}
}
}
return result;
}
步骤5，计算哈希值。将以前的比较结果，它一起构成一个64位整数，这是这张图片的指纹。组合的顺序并不重要，只要所有图片都保证在线上使用相同的顺序。以后获取指纹，您可以比较不同的图片，看看64中的多少位不一样。从理论上讲，这相当于计算“汉明距离” （汉明距离）。如果不是相同的数据位不超过5，则意味着两个图像非常相似;如果超过10，则表明这是两张不同的图片。
0111111011110011111100111110000111000001100000011110001101111010 1111111111110001111000011110000111000001100000011110000111111011