Exif Class usage

[john-giles-ff]

Hello,

I am new to the Magick.net library. It is quite an impressive piece of work.
I am working on a project where the new library has been updated to Magick.Net-Q16-AnyCPU 13.6.0

I am having trouble converting the code to work with the new library. It is mainly to do with the new Exif class and being able to set a new profile value.

The is way it was working before

        var profile = new ExifProfile();
        foreach (var exifEntry in image.ExifData)
        {
            try
            {
                if (_enum.IsDefined(typeof(ExifTag), exifEntry.Id))
                {
                    var tag = (ExifTag)exifEntry.Id;

                    object value = exifEntry.Value;

                    if ((tag == ExifTag.XResolution || tag == ExifTag.YResolution || tag == ExifTag.ExposureTime || tag == ExifTag.DigitalZoomRatio || tag == ExifTag.MaxApertureValue || tag == ExifTag.FNumber || tag == ExifTag.FocalLength || tag == ExifTag.XResolution || tag == ExifTag.YResolution || tag == ExifTag.ApertureValue))
                    {
                        if (exifEntry.Value.ToString().Contains("/"))
                        {
                            var numbers = exifEntry.Value.ToString().Split('/').Select(a => uint.Parse(a)).ToArray();
                            value = new Rational(numbers[0], numbers[1], true);
                        }
                        else ...

with profile.SetValue(tag, value);
at the end.

Now I have

        var profile = new ExifProfile();
        foreach (var exifEntry in image.ExifData)
        {
            try
            {
                if (_enum.IsDefined(typeof(ExifTagValue), exifEntry.Id))
                {
                    var tag = (ExifTagValue)exifEntry.Id;
                    object value = exifEntry.Value;

                    var magickTag = (ExifTag<ExifTagValue>)(typeof(ExifTag).GetProperty(tag.ToString()).GetValue(null, null));

                    if ((tag == ExifTagValue.XResolution || tag == ExifTagValue.YResolution || tag == ExifTagValue.ExposureTime || tag == ExifTagValue.DigitalZoomRatio || tag == ExifTagValue.MaxApertureValue || tag == ExifTagValue.FNumber || tag == ExifTagValue.FocalLength || tag == ExifTagValue.XResolution || tag == ExifTagValue.YResolution || tag == ExifTagValue.ApertureValue))
                    {
                        if (exifEntry.Value.ToString().Contains("/"))
                        {
                            var numbers = exifEntry.Value.ToString().Split('/').Select(a => uint.Parse(a)).ToArray();
                            value = new Rational(numbers[0], numbers[1], true);
                        }
                        else ...

The magickTag var is not right but I cannot see how to satisfy the command

profile.SetValue(magickTag, (ExifTagValue)value);

It may be my misunderstanding of how to use the new Exif class. I have looked through all the readme files.
Please could you point me in the right direction?

Kind regards

John

[dlemstra]

The second argument (value) should have the correct type that the specified for that specified ExifTag so depending on the type you need to typecast it. I suspect that in your case it should be (Rational)value).

[john-giles-ff]

Thank you for your response. In most cases it is Rational, however sometime it is number, Signed Rational or even byte[]
I have got a solution for now. What I have done is create a method call to determine the correct ExifTag form the passed ExifTagValue so I know what to cast the object.
There may be a better way of determining the value type and ExifTag from the ExifTagValue but I cannot think of on right now.

I have placed the code below for your interest.

Thank you again for your prompt response.

So instead of of placing
profile.SetValue(magickTag, (ExifTagValue)value);

at the end of the if else statements that parse the ExifTagValue tag into an object I call

ProfileSetValue(profile, tag, value);

Method below.

private void ProfileSetValue(ExifProfile profile, ExifTagValue tag, object value)
{
switch(tag)
{
case ExifTagValue.XResolution:
profile.SetValue(ExifTag.XResolution, (Rational)value);
break; ;

       case ExifTagValue.YResolution:
           profile.SetValue(ExifTag.YResolution, (Rational)value);
           break; ;

       case ExifTagValue.ExposureTime:
           profile.SetValue(ExifTag.ExposureTime, (Rational)value);
           break; ;

       case ExifTagValue.DigitalZoomRatio:
           profile.SetValue(ExifTag.DigitalZoomRatio, (Rational)value);
           break; ;

       case ExifTagValue.MaxApertureValue:
           profile.SetValue(ExifTag.MaxApertureValue, (Rational)value);
           break; ;

       case ExifTagValue.FNumber:
           profile.SetValue(ExifTag.XResolution, (Rational)value);
           break; ;

       case ExifTagValue.FocalLength:
           profile.SetValue(ExifTag.FocalLength, (Rational)value);
           break; ;

       case ExifTagValue.ApertureValue:
           profile.SetValue(ExifTag.ApertureValue, (Rational)value);
           break; ;

       case ExifTagValue.ISOSpeedRatings:
           profile.SetValue(ExifTag.ISOSpeedRatings, (ushort[])value);
           break; ;

       case ExifTagValue.ShutterSpeedValue:
           profile.SetValue(ExifTag.ShutterSpeedValue, (SignedRational)value);
           break; ;

       case ExifTagValue.BrightnessValue:
           profile.SetValue(ExifTag.BrightnessValue, (SignedRational)value);
           break; ;

       case ExifTagValue.ExposureBiasValue:
           profile.SetValue(ExifTag.ExposureBiasValue, (SignedRational)value);
           break; ;

       case ExifTagValue.UserComment:
           profile.SetValue(ExifTag.UserComment, (byte[])value);
           break; ;

       case ExifTagValue.ExifVersion:
           profile.SetValue(ExifTag.ExifVersion, (byte[])value);
           break; ;

       case ExifTagValue.GPSLatitude:
           profile.SetValue(ExifTag.GPSLatitude, (Rational[])value);
           break; ;

       case ExifTagValue.GPSLongitude:
           profile.SetValue(ExifTag.GPSLongitude, (Rational[])value);
           break; ;

       case ExifTagValue.ResolutionUnit:
           profile.SetValue(ExifTag.ResolutionUnit, (ushort)value);
           break; ;

       case ExifTagValue.ImageWidth:
           profile.SetValue(ExifTag.ImageWidth, (Number)value);
           break; ;

       case ExifTagValue.ImageLength:
           profile.SetValue(ExifTag.ImageLength, (Number)value);
           break; ;
   }

}

[dlemstra]

Thanks for posting here how you solved it for future readers.