Get Transparency Status on TIFF images?

[natrev]

Hi EveryOne!

Sorry for the same question again.

Is this possible to get transparency status on TIFF image using javascript? (or) is this possible via bridge script?

Whether it is checked ON/OFF( true / false ).

Any help or suggestion much appreciated.

-yajiv

[c.pfaffenbichler · Accepted solution]

I suspect this may be a fairly inefficient method, but you could give it a try:

// based on code by paul riggott;

// 2017, use it at your own risk;

var file = File.openDialog("Please select tif file.","tif File:*.tif");

main(file);

function main(file){

file.open("r");

file.encoding = 'BINARY';

filestring = file.read();

file.close();

if (filestring.indexOf("Transparency") != -1) {alert ("has transparency")}

};

[Guest]

I just wrote this code snippet which hopefully parses the TIFF file more reliably... Use it at your own risk...

//  "TIFF - Wikipedia"
//      <https://en.wikipedia.org/wiki/TIFF>
//  "TIFF™ Revision 6.0 Final — June 3, 1992"
//      <https://web.archive.org/web/20160305010142/http://partners.adobe.com/public/developer/en/tiff/TIFF6....>
//
function main ()
{
    function readInt (file, byteCount, bigEndian)
    {
        var bytes = file.read (byteCount);
        var intValue = 0;
        for (var index = 0; index < byteCount; index++)
        {
            intValue = (intValue << 8) + bytes.charCodeAt (bigEndian ? index : byteCount - index - 1);
        }
        return intValue;
    }
    //
    function isTiffFile (f)
    {
        return (f.type === 'TIFF') || f.name.match (/\.tiff?$/i);
    }
    var tiffFilter =
        (File.fs === "Macintosh") ?
            function (f) { return (f instanceof Folder) || isTiffFile (f); } :
            "TIFF Files:*.tif,All Files:*.*";
    var tiffFile = File.openDialog ("Open TIFF file:", tiffFilter);
    if (tiffFile)
    {
        var readonly = tiffFile.readonly;   // Let's work around an odd Photoshop CS bug after a file selection dialog !!
        if (tiffFile.open ('r'))
        {
            tiffFile.encoding = 'BINARY';
            var byteOrder = tiffFile.read (2);
            switch (byteOrder)
            {
                case 'II':  // IBM PC
                case 'MM':  // Macintosh
                    var bigEndian = (byteOrder === 'MM');
                    var magicNumber = readInt (tiffFile, 2, bigEndian);
                    if (magicNumber === 42) // Arbitrary but carefully chosen number...
                    {
                        var hasTransparency = false;
                        var dirOffset = readInt (tiffFile, 4, bigEndian);
                        do
                        {
                            tiffFile.seek (dirOffset);
                            var dirCount = readInt (tiffFile, 2, bigEndian);
                            for (var dirIndex = 0; dirIndex < dirCount; dirIndex++)
                            {
                                var entryTag = readInt (tiffFile, 2, bigEndian);
                                var entryType = readInt (tiffFile, 2, bigEndian);
                                var entryCount = readInt (tiffFile, 4, bigEndian);
                                var entryValueOrOffset = readInt (tiffFile, 4, bigEndian);
                                if (entryTag === 338)   // ExtraSamples
                                {
                                    if (entryType === 3)    // Short
                                    {
                                        var values = [ ];
                                        var entryTypeSize = 2;
                                        var entryValueSize = entryCount * entryTypeSize;
                                        var saveOffset = tiffFile.tell ();
                                        if (entryValueSize > 4)
                                        {
                                            tiffFile.seek (entryValueOrOffset);
                                            for (var valueIndex = 0; valueIndex < entryCount; valueIndex++)
                                            {
                                                values.push (readInt (tiffFile, entryTypeSize, bigEndian));
                                            }
                                        }
                                        else
                                        {
                                            tiffFile.seek (-4, 1);  // Rewind 4 bytes
                                            for (var valueIndex = 0; valueIndex < entryCount; valueIndex++)
                                            {
                                                values.push (readInt (tiffFile, entryTypeSize, bigEndian));
                                            }
                                        }
                                        tiffFile.seek (saveOffset);
                                        for (valueIndex = 0; valueIndex < values.length; valueIndex++)
                                        {
                                            if (values[valueIndex] === 1)   // Associated alpha data (with pre-multiplied color)
                                            {
                                                hasTransparency = true;
                                            }
                                        }
                                    }
                                    else
                                    {
                                         throw new Error ("Invalid entry type (3 expected):\n" + entryType);
                                    }
                                }
                            }
                            dirOffset = readInt (tiffFile, 4, bigEndian);
                        }
                        while (dirOffset);
                        alert ("Transparency:\n" + hasTransparency);
                    }
                    else
                    {
                        alert ("Unknown magic number:\n" + magicNumber);
                    }
                    break;
                default:
                    alert ("Unknown byte order:\n" + byteOrder);
                    break;
            }
            tiffFile.close ();
        }
        else
        {
            alert ("Cannot open TIFF file.");
        }
    }
}
//
main ();
//

[Edit]: Case of extra standard alpha channels is now correctly taken into account.

HTH,

--Mikaeru

[natrev]

Thank you Chris, 

Thank you Mikaeru69,

I have learned new thing from both of your knowledge.

I have question on mind, Same as is it possible to get Layer compression whether its Zip or RLE.

I tried but I am not able to find the solution. Any help or suggestion much appreciated.

-yajiv

[SuperMerlin]

One way is to look at the metadata.

#target photoshop;
main();
function main(){
var inputFolder = Folder.selectDialog ("Please select folder to process...");
if(inputFolder == null) return;
var myFiles = inputFolder.getFiles(/\.(tif)$/i);
for(var f = 0;f < myFiles.length;f++){
    $.writeln(decodeURI(myFiles.name) + " " + getTifCompession(myFiles));
    }
};
function getTifCompession(file){
if (ExternalObject.AdobeXMPScript == undefined) ExternalObject.AdobeXMPScript = new ExternalObject('lib:AdobeXMPScript');
var xmpf = new XMPFile(file.fsName, XMPConst.UNKNOWN, XMPConst.OPEN_FOR_READ);
var xmp = xmpf.getXMP();
 try{
var comp = xmp.getProperty( XMPConst.NS_TIFF, "Compression" ).toString();
var result = '';
switch( Number(comp) ){  
     case 1:  result = "none"; break;  
     case 5:  result = "lzw";  break;
     case 7:  result = "jpg";  break;
     case 8:  result =  "zip";  break;
     default: result =  "unknown";  
} 
return result;
}catch(e){return undefined;}
};

[natrev]

Hi SuperMerlin,

Thank you for the prompt response. The above coding is working fine and get the Image compression value (LZW, NONE,ZIP,JPEG).

However, I am asking about the Layer Compression whether ZIP or RLE.

-yajiv

[SuperMerlin]

Sorry I didn't pay attention!

I can't see a way of getting the information, I tried with a TIFF viewer TIFF Tag Viewer, Free Download

but that didn't show the required field. I wonder if Mikaeru69 knows ?

[Guest]

I just did a few investigations:

- When Layer Compression is either 'RLE' or 'ZIP', the tag 37724 gets defined (will appear in the variable entryTag in the above code).

- When Layer Compression is 'Discard', the tag 33723 is defined instead.

- According to the page TIFF tags, the tag 37724 is ImageSourceData​, privately used by Adobe Photoshop. It is described in the document Photoshop TIFF:

Adobe Photoshop specific image source data tag. This section has the layer and mask information found in a typical layered Photoshop file.

Field: ImageSourceData

Tag: 37724 (935C.H)

Type: UNDEFINED

Count: number of bytes for section

The section starts with a character string of "Adobe Photoshop Document Data Block" including the null termination character.

The remainder of the count, after subtracting the length of the above mentioned string, is a series of tagged data types in the following format:

• 4 bytes Signature ‘8BIM’
• 4 bytes Type various types (see below)
• 4 bytes Length length in bytes, variable for each type, padded to a 4 byte offset

The various types are mentioned here with further documentation in the Photoshop File Formats.pdf.

The available types are:

• ‘Layr’ Layer Data
• ‘LMsk’ User Mask     Same as Global layer mask info table
• ‘Patt’ Pattern
• ‘Anno’ Annotations

- Now, all you have to do is to consult and understand the above-mentioned document Adobe Photoshop File Formats Specification to access the relevant information... BTW, there is also a Photoshop-specific TIFF Tags section listing all the specific tags.

Good luck!

--Mikaeru

[natrev]

Hi Mikaeru,

Thank you so much for your information about TIFF tags. Now I have a clear outline on the TIFF tags and function.

-yajiv

[Stephen_A_Marsh]

A Bridge script here:

Find Layered TIFF Files