光影遮罩
這里我分類(lèi)深色與淺色遮罩，效果是什么樣呢，可以看下面的圖片,第一張是原圖，后面是遮罩圖。
[圖片上傳中...(mask.png-77d2d6-1533714162606-0)]
[圖片上傳中...(mask02.png-40df11-1533714186966-0)]
mask02.png
深色遮罩
Simulator Screen Shot - iPhone SE - 2018-08-08 at 15.46.08.png
淺色遮罩
Simulator Screen Shot - iPhone SE - 2018-08-08 at 15.54.18.png
關(guān)鍵代碼
+(UIImage *)creatImageWithMaskImage:(UIImage *)MaskImage andBackimage:(UIImage *)Backimage{
CGRect rect;
if (MaskImage.size.height>1000.0||MaskImage.size.width>1000.0)
{
rect = CGRectMake(0,
0,
MaskImage.size.width,
MaskImage.size.height);
}else{
rect = CGRectMake(0,
0,
MaskImage.size.width * 4.0,
MaskImage.size.height * 4.0);
}
CGImageRef imageRef = CGImageCreateWithImageInRect([Backimage CGImage], rect);
UIImage *cutIMG = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
//遮罩圖
CGImageRef maskImage = MaskImage.CGImage;
//原圖
CGImageRef originImage = cutIMG.CGImage;
CGContextRef mainViewContentContext;
CGColorSpaceRef colorSpace;
colorSpace = CGColorSpaceCreateDeviceRGB();
// create a bitmap graphics context the size of the image
mainViewContentContext = CGBitmapContextCreate (NULL,
rect.size.width,
rect.size.height,
8,
0,
colorSpace,
kCGImageAlphaPremultipliedLast);
// free the rgb colorspace
CGColorSpaceRelease(colorSpace);
if (mainViewContentContext==NULL)
{
// NSLog(@"error");
}
CGContextClipToMask(mainViewContentContext,
CGRectMake(0,
0,
rect.size.width,
rect.size.height),
maskImage);
CGContextDrawImage(mainViewContentContext,
CGRectMake(0,
0,
rect.size.width,
rect.size.height),
originImage);
CGContextSetAllowsAntialiasing(mainViewContentContext, true);//說(shuō)是抗鋸齒，但貌似沒(méi)用
CGContextSetShouldAntialias(mainViewContentContext, true);
// Create CGImageRef of the main view bitmap content, and then
// release that bitmap context
CGImageRef mainViewContentBitmapContext = CGBitmapContextCreateImage(mainViewContentContext);
CGContextRelease(mainViewContentContext);
// convert the finished resized image to a UIImage
UIImage *theImage = [UIImage imageWithCGImage:mainViewContentBitmapContext];
// image is retained by the property setting above, so we can
// release the original
CGImageRelease(mainViewContentBitmapContext);
return theImage;
}
首先處理新生的畫(huà)圖范圍
CGRect rect;
if (MaskImage.size.height>1000.0||MaskImage.size.width>1000.0)
{
rect = CGRectMake(0,
0,
MaskImage.size.width,
MaskImage.size.height);
}else{
rect = CGRectMake(0,
0,
MaskImage.size.width * 4.0,
MaskImage.size.height * 4.0);
}
然后我們需要把原圖和遮罩圖轉(zhuǎn)換為像素位圖
CGImageRef imageRef = CGImageCreateWithImageInRect([Backimage CGImage], rect);
UIImage *cutIMG = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
//遮罩圖
CGImageRef maskImage = MaskImage.CGImage;
//原圖
CGImageRef originImage = cutIMG.CGImage;
然后需要定義一個(gè)圖形上下文與色彩空間
CGImageRef originImage = cutIMG.CGImage;
CGContextRef mainViewContentContext;
CGColorSpaceRef colorSpace;
colorSpace = CGColorSpaceCreateDeviceRGB();
// create a bitmap graphics context the size of the image
mainViewContentContext = CGBitmapContextCreate (NULL,
rect.size.width,
rect.size.height,
8,
0,
colorSpace,
kCGImageAlphaPremultipliedLast);
// free the rgb colorspace
CGColorSpaceRelease(colorSpace);
接下來(lái)是把原圖和遮罩圖的像素位圖畫(huà)到畫(huà)布上
CGContextClipToMask(mainViewContentContext,
CGRectMake(0,
0,
rect.size.width,
rect.size.height),
maskImage);
CGContextDrawImage(mainViewContentContext,
CGRectMake(0,
0,
rect.size.width,
rect.size.height),
originImage);
CGContextSetAllowsAntialiasing(mainViewContentContext, true);//說(shuō)是抗鋸齒，但貌似沒(méi)用
CGContextSetShouldAntialias(mainViewContentContext, true);
// Create CGImageRef of the main view bitmap content, and then
// release that bitmap context
CGImageRef mainViewContentBitmapContext = CGBitmapContextCreateImage(mainViewContentContext);
CGContextRelease(mainViewContentContext);
注意要手動(dòng)去釋放已創(chuàng)建的指針。
最后是把合成后的像素位圖轉(zhuǎn)換為一般的圖片
UIImage *theImage = [UIImage imageWithCGImage:mainViewContentBitmapContext];
CGImageRelease(mainViewContentBitmapContext);
除此之外還有一種方式，也是官方文檔提到的
遮罩方法二
關(guān)鍵代碼
+(UIImage *)creatImageWithBackimage:(UIImage *)Backimage andMaskImage:(UIImage *)MaskImage
{
CGImageRef maskImage = MaskImage.CGImage;
// CGImageRef bgimage = BgImage.CGImage;
CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(maskImage), CGImageGetHeight(maskImage), CGImageGetBitsPerComponent(maskImage), CGImageGetBitsPerPixel(maskImage), CGImageGetBytesPerRow(maskImage), CGImageGetDataProvider(maskImage),NULL, false);
CGImageRef imageWithAlpha = Backimage.CGImage;
CGImageRef masked = CGImageCreateWithMask(imageWithAlpha, mask);
UIImage * newimage = [UIImage imageWithCGImage:masked];
// CGImageRelease(maskImage);
// CGImageRelease(imageWithAlpha);
CGImageRelease(masked);
return newimage;
}
從這里看的出來(lái)，相對(duì)而言簡(jiǎn)短很多。
這里使用到的關(guān)鍵是
CGImageMaskCreate(size_t width, size_t height,size_t bitsPerComponent, size_t bitsPerPixel, size_t bytesPerRow， CGDataProviderRef provider, const CGFloat decode[], bool shouldInterpolate)
sizt_t：是定義的一個(gè)可移植性的單位，在64位機(jī)器中為8字節(jié)，32位位4字節(jié)。
width：圖片寬度像素
height：圖片高度像素
bitsPerComponent：每個(gè)顏色的比特?cái)?shù)，例如在rgba-32模式下為8
bitsPerPixel：每個(gè)像素的總比特?cái)?shù)
bytesPerRow：每一行占用的字節(jié)數(shù)，注意這里的單位是字節(jié)
space：顏色空間模式，例如const CFStringRef kCGColorSpaceGenericRGB 這個(gè)函數(shù)可以返回一個(gè)顏色空間對(duì)象。
bitmapInfo：位圖像素布局，這是個(gè)枚舉
provider：數(shù)據(jù)源提供者
decode[]：解碼渲染數(shù)組
shouldInterpolate：是否抗鋸齒
intent：圖片相關(guān)參數(shù)
后面設(shè)置遮罩圖的透明通道
CGImageRef imageWithAlpha = Backimage.CGImage;
CGImageRef masked = CGImageCreateWithMask(imageWithAlpha, mask);
UIImage * newimage = [UIImage imageWithCGImage:masked];
// CGImageRelease(maskImage);
// CGImageRelease(imageWithAlpha);
CGImageRelease(masked);
PS：第二種方法和第一種的效果是相反的。
