最近因項目中缺少ios開發(fā)雌澄，臨時客串解決一些ios問題斋泄。
在一個需求中，獲取到照片的數(shù)據(jù)镐牺，將UIImage寫入文件炫掐，發(fā)現(xiàn)生成的圖片是斜的。
朝向向右睬涧，而不是向上募胃。
而用UIImageView時能顯示正常旗唁，因為UIImageView會根據(jù)圖片旋轉(zhuǎn)容器的方向。
而我們是要把圖片上傳到服務(wù)器痹束，所以這個不行检疫。
然后在網(wǎng)上找到的辦法如下：(不行)
+ (UIImage *)fixOrientation:(UIImage *)aImage {
// No-op if the orientation is already correct
if (aImage.imageOrientation ==UIImageOrientationUp)
return aImage;
// We need to calculate the proper transformation to make the image upright.
// We do it in 2 steps: Rotate if Left/Right/Down, and then flip if Mirrored.
CGAffineTransform transform =CGAffineTransformIdentity;
switch (aImage.imageOrientation) {
caseUIImageOrientationDown:
caseUIImageOrientationDownMirrored:
transform = CGAffineTransformTranslate(transform, aImage.size.width, aImage.size.height);
transform = CGAffineTransformRotate(transform, M_PI);
break;
caseUIImageOrientationLeft:
caseUIImageOrientationLeftMirrored:
transform = CGAffineTransformTranslate(transform, aImage.size.width,0);
transform = CGAffineTransformRotate(transform, M_PI_2);
break;
caseUIImageOrientationRight:
caseUIImageOrientationRightMirrored:
transform = CGAffineTransformTranslate(transform, 0, aImage.size.height);
transform = CGAffineTransformRotate(transform, -M_PI_2);
break;
default:
break;
}
switch (aImage.imageOrientation) {
caseUIImageOrientationUpMirrored:
caseUIImageOrientationDownMirrored:
transform = CGAffineTransformTranslate(transform, aImage.size.width,0);
transform = CGAffineTransformScale(transform, -1, 1);
break;
caseUIImageOrientationLeftMirrored:
caseUIImageOrientationRightMirrored:
transform = CGAffineTransformTranslate(transform, aImage.size.height,0);
transform = CGAffineTransformScale(transform, -1, 1);
break;
default:
break;
}
// Now we draw the underlying CGImage into a new context, applying the transform
// calculated above.
CGContextRef ctx =CGBitmapContextCreate(NULL, aImage.size.width, aImage.size.height,
CGImageGetBitsPerComponent(aImage.CGImage),0,
CGImageGetColorSpace(aImage.CGImage),
CGImageGetBitmapInfo(aImage.CGImage));
CGContextConcatCTM(ctx, transform);
switch (aImage.imageOrientation) {
caseUIImageOrientationLeft:
caseUIImageOrientationLeftMirrored:
caseUIImageOrientationRight:
caseUIImageOrientationRightMirrored:
// Grr...
CGContextDrawImage(ctx,CGRectMake(0,0,aImage.size.height,aImage.size.width), aImage.CGImage);
break;
default:
CGContextDrawImage(ctx,CGRectMake(0,0,aImage.size.width,aImage.size.height), aImage.CGImage);
break;
}
// And now we just create a new UIImage from the drawing context
CGImageRef cgimg =CGBitmapContextCreateImage(ctx);
UIImage *img = [UIImageimageWithCGImage:cgimg];
CGContextRelease(ctx);
CGImageRelease(cgimg);
return img;
}
該方法不行，在斷點調(diào)試時發(fā)現(xiàn)祷嘶，是因為該圖片UIImage的朝向就是 UIImageOrientationUp屎媳。
也就是在已進(jìn)入這個方法時就return了，下面的都沒有執(zhí)行论巍。
但我們視覺看到的確實是朝向不對烛谊，代碼檢測的卻是朝向上。
所以導(dǎo)致該方法不行嘉汰，我試過去屏蔽掉第一句的判斷以及return丹禀。但是生成的圖片白屏。
還是過其他的辦法鞋怀，發(fā)現(xiàn)有的是能旋轉(zhuǎn)過來双泪，但圖片的寬高會有問題，導(dǎo)致圖片在寬度上被拉伸密似，高度上被壓縮焙矛，
即圖片的寬高沒有對換。
然后發(fā)現(xiàn)一個方法： quartz2D來畫圖片辛友，然后使用ctm變幻來實現(xiàn)旋轉(zhuǎn)
原文地址：https://blog.csdn.net/bitcser/article/details/52055442?utm_source=blogxgwz4
代碼如下：
+(UIImage *)image:(UIImage *)image rotation:(UIImageOrientation)orientation
{
long double rotate = 0.0;
CGRect rect;
float translateX = 0;
float translateY = 0;
float scaleX = 1.0;
float scaleY = 1.0;
switch (orientation) {
case UIImageOrientationLeft:
rotate =M_PI_2;
rect =CGRectMake(0,0,image.size.height, image.size.width);
translateX=0;
translateY= -rect.size.width;
scaleY =rect.size.width/rect.size.height;
scaleX =rect.size.height/rect.size.width;
break;
case UIImageOrientationRight:
rotate =3 *M_PI_2;
rect =CGRectMake(0,0,image.size.height, image.size.width);
translateX= -rect.size.height;
translateY=0;
scaleY =rect.size.width/rect.size.height;
scaleX =rect.size.height/rect.size.width;
break;
case UIImageOrientationDown:
rotate =M_PI;
rect =CGRectMake(0,0,image.size.width, image.size.height);
translateX= -rect.size.width;
translateY= -rect.size.height;
break;
default:
rotate =0.0;
rect =CGRectMake(0,0,image.size.width, image.size.height);
translateX=0;
translateY=0;
break;
}
UIGraphicsBeginImageContext(rect.size);
CGContextRef context =UIGraphicsGetCurrentContext();
//做CTM變換
CGContextTranslateCTM(context, 0.0, rect.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextRotateCTM(context, rotate);
CGContextTranslateCTM(context, translateX,translateY);
CGContextScaleCTM(context, scaleX,scaleY);
//繪制圖片
CGContextDrawImage(context, CGRectMake(0,0,rect.size.width, rect.size.height), image.CGImage);
UIImage *newPic =UIGraphicsGetImageFromCurrentImageContext();
return newPic;
}
