iOS Question Image.Rotate Strange behavior

Mike1970 · Dec 17, 2020

Hi everyone.

From today the instruction .Rotate for a bitmap is behaving in a strange way.
I think the only thing changed is that I update to iOS 14.3.

My tests
The code

B4X:

Sub Cam_Complete(Success As Boolean, Image as Bitmap, VideoPath As String)
    If Success Then
        If Image.IsInitialized Then
            btnDelete_Click 'delete previous chached images'
         
            imgCL.ContentMode = imgCL.MODE_FIT
            imgCL.Bitmap = Image

            Dim out as OutputStream = File.OpenOutput(path, fname, False)
            Image.Rotate(90).WriteToStream(out, 50, "JPEG")
         
            Dim p as Phone
            p.AddImageToAlbum(LoadBitmap(path, fname))
         
        End If
    End If
End Sub

This code ☝result is this image:

I changed the line 10 to:

B4X:

Image.WriteToStream(out, 50, "JPEG")

then I recompiled the app, and take another shot.

and the result was this:

this is the right real-life aspect

Small video and project example in post #8

agraham · Dec 17, 2020

I'm not sure if you are joking but the second image is a completely different image to the first. Look elsewhere in your code for whatever the problem is.

Mike1970 · Dec 17, 2020

agraham said:
I'm not sure if you are joking but the second image is a completely different image to the first. Look elsewhere in your code for whatever the problem is.

it's only a different shot -.-

1. i compiled the app
2. I take the shot
3. I changed the line
4. i re-compiled the app
5. i taked another shot of the SAME subject just to show the differences

I'm not stupid .-.

agraham · Dec 17, 2020

Sorry but I still don't understand your problem?

Mike1970 · Dec 17, 2020

agraham said:
Sorry but I still don't understand your problem?

ok... if you take a closer look to the two images, you can immediately notice that the RESULT image when I use ".Rotate(90)" it is SQUEEZED on the Y Axes (instead of rotated 90° however).

If I remove the ".Rotate(90)" function the image result it's correct, no squeezing, no stretching.

As soon as Windows finishes the update, i try to execute the same app on an iPhone5 with iOS 11 I think

Pendrush · Dec 17, 2020

You should use same image in example, not two different images.

Mike1970 · Dec 17, 2020

Pendrush said:
You should use same image in example, not two different images.

The problems occurs when I take a shot.
The function "Cam_Complete" is called when I just finished to call the OS Camera API

Mike1970 · Dec 17, 2020

@Pendrush , @agraham
I made a test project, and a video to show the problem.

Link to watch the video on MEGA: https://mega.nz/file/HZ0CQLRS#YlBIQvItD4Aqjo54z4o70veIk14yD4KH990c3BXCVSk

Before you said
the variant:

B4X:

dim im as bitmap = Image.Rotate(90)
im.WriteToStream(out, 50, "JPEG")

behave the same

agraham · Dec 17, 2020

The effect is much more obvious in the video than in the original photos, where I still can't really see the stretching despite now knowing what to look for! My guess is that it is due to the EXIF information regarding the camera orientation when the photo was taken.

It is possible that the effect is caused when displaying the photo and not when saving it as the image jpg might contain conflicting width/height/EXIF information but it would need further testing to check this out. First thing I would do is put the image on a PC and display it with several different image viewers and also look at the EXIF data for the normal and the stretched versions.

Mike1970 · Dec 17, 2020

agraham said:
where I still can't really see the stretching despite now knowing what to look for!

I put both the images in the first post just to give to all of you a reference. I thought it was clear that the first photo isn't representing the real-world in a correct way ?... compared to the one I classified like "the good one" (the second).
(just compare the height and width of the two images... )

agraham said:
First thing I would do is put the image on a PC and display it with several different image viewers

In the original project, the image file (the same I save in the Photo app of the iPhone) is sent to an FTP Server.
For obvious reasons I did not implemented this in the demo project.

however, the images are displayed in the same way on Pc too, I verified it by downloading the images from the FTP Server

Mike1970 · Dec 17, 2020

I tried this tool: http://exif.regex.info/exif.cgi
~~with the image I attach.~~ I can't upload the image, it too large..
It says "horizontal" as orientation

agraham · Dec 17, 2020

The only thing I can suggest is that you try saving without rotation then reload an image from the file, rotate it and save again to see if that makes any difference.

Mike1970 · Dec 17, 2020

agraham said:
The only thing I can suggest is that you try saving without rotation then reload an image from the file, rotate it and save again to see if that makes any difference.

Technically should be similar to this

Mike1970 said:
B4X:

dim im as bitmap = Image.Rotate(90) im.WriteToStream(out, 50, "JPEG")

however I try

Mike1970 · Dec 17, 2020

@agraham i modified the Example by changing the "Cam_complete" function to:

B4X:

Sub Cam_Complete (Success As Boolean, image As Bitmap, VideoPath As String)
    If Success Then
        If image.IsInitialized Then
          
            imageview.ContentMode = imageview.MODE_FIT
            imageview.Bitmap = image
          
            Dim out As OutputStream = File.OpenOutput(File.DirLibrary & "/" & "TestBitmap", "bitmap.jpeg", False)
            image.WriteToStream(out, 50, "JPEG") 
            out.Close
          
            Dim im As Bitmap = LoadBitmap(File.DirLibrary & "/" & "TestBitmap", "bitmap.jpeg")
            If Switch1.Value Then
                im = im.Rotate(90)
            End If
          
            Dim p As Phone
            p.AddImageToAlbum(im)
        End If
    End If
End Sub

So the image saved to Album is alwasy an image loaded from the memory.
If the switch is on, then before save the image to the Album it rotates

the result is the same... stretch

agraham · Dec 18, 2020

Mike1970 said:
Technically should be similar to this

Not necessarily, it depends on how the EXIF data is treated within an Image and written to file.

However you haven't done what I suggested and saved the rotated image to file and then reloaded it to see if it makes a difference. You have only rotated the image in memory. I don't really expect a difference as maybe rotate() is broken but try it anyway.

Mike1970 · Dec 18, 2020

agraham said:
You have only rotated the image in memory.

So you mean rotate and THEN WriteToStream

agraham · Dec 18, 2020

Mike1970 said:
So you mean rotate and THEN WriteToStream

Yes.

Mike1970 · Dec 18, 2020

agraham said:
Yes.

This is the updated function. Same result. when the switch is on, the image is squeezed instead of rotated

B4X:

Sub Cam_Complete (Success As Boolean, image As Bitmap, VideoPath As String)
    If Success Then
        If image.IsInitialized Then
                      
            If Switch1.Value Then
                image = image.Rotate(90)
            End If
          
            imageview.ContentMode = imageview.MODE_FIT
            imageview.Bitmap = image
          
            Dim out As OutputStream = File.OpenOutput(File.DirLibrary & "/" & "TestBitmap", "bitmap.jpeg", False)
            image.WriteToStream(out, 50, "JPEG") 
            out.Close
          
            Dim p As Phone
            p.AddImageToAlbum(image)
        End If
    End If
End Sub

angel_ · Dec 18, 2020

Mike1970 said:

This is the updated function. Same result. when the switch is on, the image is squeezed instead of rotated

B4X:

Sub Cam_Complete (Success As Boolean, image As Bitmap, VideoPath As String)
    If Success Then
        If image.IsInitialized Then
                     
            If Switch1.Value Then
                image = image.Rotate(90)
            End If
         
            imageview.ContentMode = imageview.MODE_FIT
            imageview.Bitmap = image
         
            Dim out As OutputStream = File.OpenOutput(File.DirLibrary & "/" & "TestBitmap", "bitmap.jpeg", False)
            image.WriteToStream(out, 50, "JPEG")
            out.Close
         
            Dim p As Phone
            p.AddImageToAlbum(image)
        End If
    End If
End Sub

Try putting the imageview inside a panel and rotating the panel

Mike1970 · Dec 18, 2020

angel_ said:
Try putting the imageview inside a panel and rotating the panel

I can't do it for two reasons.
1. I don't know how to rotate a panel ? (no the main problem)
2. I need the FILE, because I need to send the image via FTP then. (the true reason), so I need to actually manipulate the image file.

iOS Question Image.Rotate Strange behavior

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