[英]How to create a mask from an image
我在NSbundle中有一張圖片。 下面是圖片
http://tinypic.com/view.php?pic=2093tvt&s=5
我想將此圖像用作遮罩圖像,並希望將其應用於任何圖像,以便其他圖像將具有與上述圖像相同的形狀。
所以這是一個重復的問題,但對我不起作用。
正如上面的問題,建議對圖像進行縮放,所以我也這樣做了。 我通過代碼將圖像更改為灰度
- (UIImage *) convertToGreyscale:(UIImage *)i {
int kRed = 1;
int kGreen = 2;
int kBlue = 4;
int colors = kGreen;
int m_width = i.size.width;
int m_height = i.size.height;
uint32_t *rgbImage = (uint32_t *) malloc(m_width * m_height * sizeof(uint32_t));
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(rgbImage, m_width, m_height, 8, m_width * 4, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipLast);
CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
CGContextSetShouldAntialias(context, NO);
CGContextDrawImage(context, CGRectMake(0, 0, m_width, m_height), [i CGImage]);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
// now convert to grayscale
uint8_t *m_imageData = (uint8_t *) malloc(m_width * m_height);
for(int y = 0; y < m_height; y++) {
for(int x = 0; x < m_width; x++) {
uint32_t rgbPixel=rgbImage[y*m_width+x];
uint32_t sum=0,count=0;
if (colors & kRed) {sum += (rgbPixel>>24)&255; count++;}
if (colors & kGreen) {sum += (rgbPixel>>16)&255; count++;}
if (colors & kBlue) {sum += (rgbPixel>>8)&255; count++;}
m_imageData[y*m_width+x]=sum/count;
}
}
free(rgbImage);
// convert from a gray scale image back into a UIImage
uint8_t *result = (uint8_t *) calloc(m_width * m_height *sizeof(uint32_t), 1);
// process the image back to rgb
for(int i = 0; i < m_height * m_width; i++) {
result[i*4]=0;
int val=m_imageData[i];
result[i*4+1]=val;
result[i*4+2]=val;
result[i*4+3]=val;
}
// create a UIImage
colorSpace = CGColorSpaceCreateDeviceRGB();
context = CGBitmapContextCreate(result, m_width, m_height, 8, m_width * sizeof(uint32_t), colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipLast);
CGImageRef image = CGBitmapContextCreateImage(context);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
UIImage *resultUIImage = [UIImage imageWithCGImage:image];
CGImageRelease(image);
free(m_imageData);
// make sure the data will be released by giving it to an autoreleased NSData
[NSData dataWithBytesNoCopy:result length:m_width * m_height];
return resultUIImage;
}
下面是灰度圖像
鏈接1:
當我遮蓋圖像時,結果我得到的結果低於注釋中給出的鏈接。 我不能添加超過2個鏈接
鏈接2:
我想我沒有創建適當的蒙版圖像
我正在嘗試遮蓋圖片http://tinypic.com/view.php?pic=10di24m&s=5
有人可以告訴我制作遮罩圖像的方法嗎?
您所使用的方法Graysclae似乎存在問題,它使圓圈外的顏色變為黑色,但應將其設置為白色以正確掩蓋它。
這是我寫的圖像類別
UIImage + Mask.h
#import <UIKit/UIKit.h>
@interface UIImage (Mask)
- (UIImage*) maskImage:(UIImage *) image;
- (UIImage *)greyscaleImage;
@end
UIImage + Mask.m
@implementation UIImage (Mask)
- (UIImage*) maskImage:(UIImage *) image
{
CGImageRef imageReference = image.CGImage;
CGImageRef maskReference = self.CGImage;
CGImageRef imageMask = CGImageMaskCreate(CGImageGetWidth(maskReference),
CGImageGetHeight(maskReference),
CGImageGetBitsPerComponent(maskReference),
CGImageGetBitsPerPixel(maskReference),
CGImageGetBytesPerRow(maskReference),
CGImageGetDataProvider(maskReference),
NULL, // Decode is null
YES // Should interpolate
);
CGImageRef maskedReference = CGImageCreateWithMask(imageReference, imageMask);
CGImageRelease(imageMask);
UIImage *maskedImage = [UIImage imageWithCGImage:maskedReference];
CGImageRelease(maskedReference);
return maskedImage;
}
- (UIImage *)greyscaleImage {
CGImageRef imgRef = self.CGImage;
// Get the image width
CGFloat width = CGImageGetWidth(imgRef);
CGFloat height = CGImageGetHeight(imgRef);
// Create a Grayscale colour space
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
/*
* Create the context - based on orientation
*/
CGContextRef context = nil;
// If the orientation isn't UIImageOrientationUp then we'll need to rotate
UIImageOrientation orient = self.imageOrientation;
switch (orient) {
case UIImageOrientationUp:
case UIImageOrientationDown:
case UIImageOrientationDownMirrored:
case UIImageOrientationUpMirrored:
context = CGBitmapContextCreate(NULL, width, height, 8, 0, colorSpace, kCGImageAlphaNone);
break;
default:
context = CGBitmapContextCreate(NULL, height, width, 8, 0, colorSpace, kCGImageAlphaNone);
break;
}
CGColorSpaceRelease(colorSpace);
/*
* Create a context translation/rotation based on the orientation
*/
switch(orient) {
case UIImageOrientationUpMirrored:
// 2 = 0th row is at the top, and 0th column is on the right - Flip Horizontal
CGContextConcatCTM(context, CGAffineTransformMake(-1.0, 0.0, 0.0, 1.0, width, 0.0));
break;
case UIImageOrientationDown:
// 3 = 0th row is at the bottom, and 0th column is on the right - Rotate 180 degrees
CGContextConcatCTM(context, CGAffineTransformMake(-1.0, 0.0, 0.0, -1.0, width, height));
break;
case UIImageOrientationDownMirrored:
// 4 = 0th row is at the bottom, and 0th column is on the left - Flip Vertical
CGContextConcatCTM(context, CGAffineTransformMake(1.0, 0.0, 0, -1.0, 0.0, height));
break;
case UIImageOrientationLeftMirrored:
// 5 = 0th row is on the left, and 0th column is the top - Rotate -90 degrees and Flip Vertical
CGContextConcatCTM(context, CGAffineTransformMake(0.0, -1.0, -1.0, 0.0, height, width));
break;
case UIImageOrientationRight:
// 6 = 0th row is on the right, and 0th column is the top - Rotate 90 degrees
CGContextConcatCTM(context, CGAffineTransformMake(0.0, -1.0, 1.0, 0.0, 0.0, width));
break;
case UIImageOrientationRightMirrored:
// 7 = 0th row is on the right, and 0th column is the bottom - Rotate 90 degrees and Flip Vertical
CGContextConcatCTM(context, CGAffineTransformMake(0.0, 1.0, 1.0, 0.0, 0.0, 0.0));
break;
case UIImageOrientationLeft:
// 8 = 0th row is on the left, and 0th column is the bottom - Rotate -90 degrees
CGContextConcatCTM(context, CGAffineTransformMake(0.0, 1.0, -1.0, 0.0, height, 0.0));
break;
case UIImageOrientationUp:
// Nothing to do here
break;
}
/*
* Create the new image
*/
CGContextSetFillColorWithColor(context, [UIColor whiteColor].CGColor);
CGContextFillRect(context, CGRectMake(0, 0, width, height));
//CGContextFillEllipseInRect(context, );
// Draw the image to the context
CGContextDrawImage(context, CGRectMake(0, 0, width, height), imgRef);
// Get a UIImage from the context
CGImageRef imageRef = CGBitmapContextCreateImage(context);
UIImage *imageCopy = [UIImage imageWithCGImage:imageRef];
// Release
CGImageRelease(imageRef);
CGContextRelease(context);
return imageCopy;
}
@end
這是用法
UIImage *maskImage = [UIImage imageNamed:@"maskimage"]; // in your case the red dot image
UIImage *image = [UIImage imageNamed:@"image"]; // image to mask
maskImage = [maskImage greyscaleImage];
image = [maskImage maskImage:image];
self.imageView.image = image;
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