我正在制作一个应用程序来通过 opencv2 和来自 Internet 的一些转换代码来编辑图像的 HSL 颜色空间。
我想原始图像的色彩空间是 RGB，所以这是我的想法：
- 将 UIImage 转换为 cvMat
- 将色彩空间从 BGR 转换为 HLS。
- 循环遍历所有像素点，得到对应的 HLS 值。
- 自定义算法。
- 将 HLS 值更改重写为 cvMat
- 将 cvMat 转换为 UIImage
这是我的代码：
UIImage 和 cvMat 之间的转换
参考：https ://stackoverflow.com/a/10254561/1677041
#import <UIKit/UIKit.h>
#import <opencv2/core/core.hpp>
UIImage *UIImageFromCVMat(cv ::Mat cvMat)
{
NSData *data = [NSData dataWithBytes:cvMat.data length:cvMat.elemSize() * cvMat.total()];
CGColorSpaceRef colorSpace;
CGBitmapInfo bitmapInfo;
if (cvMat.elemSize() == 1) {
colorSpace = CGColorSpaceCreateDeviceGray();
bitmapInfo = kCGImageAlphaNone | kCGBitmapByteOrderDefault;
} else {
colorSpace = CGColorSpaceCreateDeviceRGB();
#if 0
// OpenCV defaults to either BGR or ABGR. In CoreGraphics land,
// this means using the "32Little" byte order, and potentially
// skipping the first pixel. These may need to be adjusted if the
// input matrix uses a different pixel format.
bitmapInfo = kCGBitmapByteOrder32Little | (
cvMat.elemSize() == 3? kCGImageAlphaNone : kCGImageAlphaNoneSkipFirst
);
#else
bitmapInfo = kCGImageAlphaNone | kCGBitmapByteOrderDefault;
#endif
}
CGDataProviderRef provider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data);
// Creating CGImage from cv::Mat
CGImageRef imageRef = CGImageCreate(
cvMat.cols, // width
cvMat.rows, // height
8, // bits per component
8 * cvMat.elemSize(), // bits per pixel
cvMat.step[0], // bytesPerRow
colorSpace, // colorspace
bitmapInfo, // bitmap info
provider, // CGDataProviderRef
NULL, // decode
false, // should interpolate
kCGRenderingIntentDefault // intent
);
// Getting UIImage from CGImage
UIImage *finalImage = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
CGDataProviderRelease(provider);
CGColorSpaceRelease(colorSpace);
return finalImage;
}
cv::Mat cvMatWithImage(UIImage *image)
{
CGColorSpaceRef colorSpace = CGImageGetColorSpace(image.CGImage);
size_t numberOfComponents = CGColorSpaceGetNumberOfComponents(colorSpace);
CGFloat cols = image.size.width;
CGFloat rows = image.size.height;
cv::Mat cvMat(rows, cols, CV_8UC4); // 8 bits per component, 4 channels
CGBitmapInfo bitmapInfo = kCGImageAlphaNoneSkipLast | kCGBitmapByteOrderDefault;
// check whether the UIImage is greyscale already
if (numberOfComponents == 1) {
cvMat = cv::Mat(rows, cols, CV_8UC1); // 8 bits per component, 1 channels
bitmapInfo = kCGImageAlphaNone | kCGBitmapByteOrderDefault;
}
CGContextRef contextRef = CGBitmapContextCreate(
cvMat.data, // Pointer to backing data
cols, // Width of bitmap
rows, // Height of bitmap
8, // Bits per component
cvMat.step[0], // Bytes per row
colorSpace, // Colorspace
bitmapInfo // Bitmap info flags
);
CGContextDrawImage(contextRef, CGRectMake(0, 0, cols, rows), image.CGImage);
CGContextRelease(contextRef);
return cvMat;
}
我单独测试了这两个功能并确认它们有效。
关于转换的核心操作：
/// Generate a new image based on specified HSL value changes.
/// @param h_delta h value in [-360, 360]
/// @param s_delta s value in [-100, 100]
/// @param l_delta l value in [-100, 100]
- (void)adjustImageWithH:(CGFloat)h_delta S:(CGFloat)s_delta L:(CGFloat)l_delta completion:(void (^)(UIImage *resultImage))completion
{
dispatch_async(dispatch_get_global_queue(0, 0), ^{
Mat original = cvMatWithImage(self.originalImage);
Mat image;
cvtColor(original, image, COLOR_BGR2HLS);
// https://docs.opencv.org/2.4/doc/tutorials/core/how_to_scan_images/how_to_scan_images.html#the-efficient-way
// accept only char type matrices
CV_Assert(image.depth() == CV_8U);
int channels = image.channels();
int nRows = image.rows;
int nCols = image.cols * channels;
int y, x;
for (y = 0; y < nRows; ++y) {
for (x = 0; x < nCols; ++x) {
// https://answers.opencv.org/question/30547/need-to-know-the-hsv-value/
// https://docs.opencv.org/2.4/modules/imgproc/doc/miscellaneous_transformations.html?#cvtcolor
Vec3b hls = original.at<Vec3b>(y, x);
uchar h = hls.val[0], l = hls.val[1], s = hls.val[2];
// h = MAX(0, MIN(360, h + h_delta));
// s = MAX(0, MIN(100, s + s_delta));
// l = MAX(0, MIN(100, l + l_delta));
printf("(%02d, %02d):\tHSL(%d, %d, %d)\n", x, y, h, s, l); // <= Label 1
original.at<Vec3b>(y, x)[0] = h;
original.at<Vec3b>(y, x)[1] = l;
original.at<Vec3b>(y, x)[2] = s;
}
}
cvtColor(image, image, COLOR_HLS2BGR);
UIImage *resultImage = UIImageFromCVMat(image);
dispatch_async(dispatch_get_main_queue(), ^ {
if (completion) {
completion(resultImage);
}
});
});
}
问题是：
- 为什么 HLS 值超出我的预期范围？它显示为 [0, 255] 像 RGB 范围，是 cvtColor 错误使用吗？
- 我应该在两个 for 循环中使用 Vec3b 吗？还是 Vec3i？
- 我的想法上面有什么问题吗？
更新：
Vec3b hls = original.at<Vec3b>(y, x);
uchar h = hls.val[0], l = hls.val[1], s = hls.val[2];
// Remap the hls value range to human-readable range (0~360, 0~1.0, 0~1.0).
// https://docs.opencv.org/master/de/d25/imgproc_color_conversions.html
float fh, fl, fs;
fh = h * 2.0;
fl = l / 255.0;
fs = s / 255.0;
fh = MAX(0, MIN(360, fh + h_delta));
fl = MAX(0, MIN(1, fl + l_delta / 100));
fs = MAX(0, MIN(1, fs + s_delta / 100));
// Convert them back
fh /= 2.0;
fl *= 255.0;
fs *= 255.0;
printf("(%02d, %02d):\tHSL(%d, %d, %d)\tHSL2(%.4f, %.4f, %.4f)\n", x, y, h, s, l, fh, fs, fl);
original.at<Vec3b>(y, x)[0] = short(fh);
original.at<Vec3b>(y, x)[1] = short(fl);
original.at<Vec3b>(y, x)[2] = short(fs);