我尝试将图片从手机上传到我的网络服务，并注意到上传图片时图片方向已丢失。在上传之前我是否需要做些什么才能确保以正确的方向上传图片？
我也在其他地方看了一下，发现了Objective-C代码来旋转我转换成C＃的图像，但是每次使用旋转方法时，图像都会变黑，即我猜不出任何东西。
我附上我的代码供您参考，如果有人能告诉我我做错了什么，我真的很感激。谢谢！
public static UIImage RotateImage(this UIImage image)
{
UIImage imageToReturn = null;
if(image.Orientation == UIImageOrientation.Up)
{
imageToReturn = image;
}
else
{
CGAffineTransform transform = CGAffineTransform.MakeIdentity();
switch (image.Orientation) {
case UIImageOrientation.Down:
case UIImageOrientation.DownMirrored:
transform.Translate(image.Size.Width, image.Size.Height);
transform.Rotate((float)Math.PI);
break;
case UIImageOrientation.Left:
case UIImageOrientation.LeftMirrored:
transform.Translate(image.Size.Width, 0);
transform.Rotate((float)Math.PI/2);
break;
case UIImageOrientation.Right:
case UIImageOrientation.RightMirrored:
transform.Translate(0, image.Size.Height);
transform.Rotate((float)-Math.PI/2);
break;
case UIImageOrientation.Up:
case UIImageOrientation.UpMirrored:
break;
}
switch (image.Orientation) {
case UIImageOrientation.UpMirrored:
case UIImageOrientation.DownMirrored:
transform.Translate(image.Size.Width, 0);
transform.Scale(-1, 1);
break;
case UIImageOrientation.LeftMirrored:
case UIImageOrientation.RightMirrored:
transform.Translate(image.Size.Height, 0);
transform.Scale(-1, 1);
break;
case UIImageOrientation.Up:
case UIImageOrientation.Down:
case UIImageOrientation.Left:
case UIImageOrientation.Right:
break;
}
//now draw image
using(var context = new CGBitmapContext(IntPtr.Zero,
(int)image.Size.Width,
(int)image.Size.Height,
image.CGImage.BitsPerComponent,
image.CGImage.BytesPerRow,
image.CGImage.ColorSpace,
image.CGImage.BitmapInfo)){
context.ConcatCTM(transform);
switch (image.Orientation)
{
case UIImageOrientation.Left:
case UIImageOrientation.LeftMirrored:
case UIImageOrientation.Right:
case UIImageOrientation.RightMirrored:
// Grr...
context.DrawImage(new RectangleF(PointF.Empty,new SizeF(image.Size.Height, image.Size.Width)), image.CGImage);
break;
default:
context.DrawImage(new RectangleF(PointF.Empty, new SizeF(image.Size.Width, image.Size.Height)), image.CGImage);
break;
}
using(var imageRef = context.ToImage())
{
imageToReturn = new UIImage(imageRef);
}
}
}
return imageToReturn;
}
答案 0 :(得分：3)
你获得黑色图像的原因是翻译和旋转调用是向后的。 iPod / iphone上的普通人像照片处于“正确”方向。转换它们的正确代码使用：
case UIImageOrientation.Right:
case UIImageOrientation.RightMirrored:
transform.Rotate (-(float)Math.PI / 2);
transform.Translate (0, input.Size.Height);
break;
转换函数依赖于顺序。此代码将其旋转到正确的方向，但由于旋转大约是左下方的0,0坐标，因此图像现在刚好在框架的底部。翻译然后将它推到它所属的位置。
原始代码会将侧面图像从框架顶部推开，然后旋转会使图像向右转，但是会偏离框架的右侧。
使用较小的高度值，如100或200和pi / 4，可以轻松显示更改这些功能的顺序时所获得的差异，因为某些原始图像将始终可见。
答案 1 :(得分：1)
使用@Random提供的信息，我更正了原始代码：
private byte[] RotateImage(UIImage image)
{
UIImage imageToReturn = null;
if (image.Orientation == UIImageOrientation.Up)
{
imageToReturn = image;
}
else
{
CGAffineTransform transform = CGAffineTransform.MakeIdentity();
switch (image.Orientation)
{
case UIImageOrientation.Down:
case UIImageOrientation.DownMirrored:
transform.Rotate((float)Math.PI);
transform.Translate(image.Size.Width, image.Size.Height);
break;
case UIImageOrientation.Left:
case UIImageOrientation.LeftMirrored:
transform.Rotate((float)Math.PI / 2);
transform.Translate(image.Size.Width, 0);
break;
case UIImageOrientation.Right:
case UIImageOrientation.RightMirrored:
transform.Rotate(-(float)Math.PI / 2);
transform.Translate(0, image.Size.Height);
break;
case UIImageOrientation.Up:
case UIImageOrientation.UpMirrored:
break;
}
switch (image.Orientation)
{
case UIImageOrientation.UpMirrored:
case UIImageOrientation.DownMirrored:
transform.Translate(image.Size.Width, 0);
transform.Scale(-1, 1);
break;
case UIImageOrientation.LeftMirrored:
case UIImageOrientation.RightMirrored:
transform.Translate(image.Size.Height, 0);
transform.Scale(-1, 1);
break;
case UIImageOrientation.Up:
case UIImageOrientation.Down:
case UIImageOrientation.Left:
case UIImageOrientation.Right:
break;
}
//now draw image
using (var context = new CGBitmapContext(IntPtr.Zero,
(int)image.Size.Width,
(int)image.Size.Height,
image.CGImage.BitsPerComponent,
image.CGImage.BytesPerRow,
image.CGImage.ColorSpace,
image.CGImage.BitmapInfo))
{
context.ConcatCTM(transform);
switch (image.Orientation)
{
case UIImageOrientation.Left:
case UIImageOrientation.LeftMirrored:
case UIImageOrientation.Right:
case UIImageOrientation.RightMirrored:
// Grr...
context.DrawImage(new RectangleF(PointF.Empty, new SizeF((float)image.Size.Height, (float)image.Size.Width)), image.CGImage);
break;
default:
context.DrawImage(new RectangleF(PointF.Empty, new SizeF((float)image.Size.Width, (float)image.Size.Height)), image.CGImage);
break;
}
using (var imageRef = context.ToImage())
{
imageToReturn = new UIImage(imageRef);
}
}
}
using (NSData imageData = imageToReturn.AsJPEG())
{
Byte[] byteArray = new Byte[imageData.Length];
System.Runtime.InteropServices.Marshal.Copy(imageData.Bytes, byteArray, 0, Convert.ToInt32(imageData.Length));
return byteArray;
}
}
非常有用的代码
答案 2 :(得分：0)
我通过this gist找到了this question。希望这段代码适合你！