> For the complete documentation index, see [llms.txt](https://docs.apryse.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.apryse.com/ios/editing-page-content/graphics-state.md).

# Graphics state on iOS

Learn how to extract data from PDF files, including images, text, and paths. Explore a full code sample for PDF data extraction and processing changes in the graphics state efficiently with Apryse SDK

To traverse the list of changes in the graphics state.

{% tabs %}
{% tab title="Obj-C" %}
{% code lineNumbers="true" %}

```objc
PTGSChangesIterator *gs_itr = [reader GetChangesIterator];
for (; [gs_itr HasNext]; [gs_itr Next]) 
{
  switch([gs_itr Current])
  {
    case e_pttransform :
      // Get transform matrix for this element. Unlike path.GetCTM() 
      // that return full transformation matrix gs.GetTransform() return 
      // only the transformation matrix that was installed for this element.
      //
      // gs.GetTransform();
      break;
    case e_ptline_width :
      // gs.GetLineWidth();
      break;
    case e_ptline_cap :
      // gs.GetLineCap();
      break;
    case e_ptline_join :
      // gs.GetLineJoin();
      break;
    case e_ptmiter_limit :
      // gs.GetMiterLimit();
      break;
    case e_ptdash_pattern :
      {
        // std::vector<double> dashes;
        // gs.GetDashes(dashes);
        // gs.GetPhase()
      }
      break;
    default:
      break;
  }
}
```

{% endcode %}
{% endtab %}

{% tab title="Swift" %}
{% code lineNumbers="true" %}

```swift
let gs_itr: PTGSChangesIterator = reader.getChangesIterator()
while gs_itr.hasNext() {
  switch PTGStateAttribute(rawValue: UInt32(gs_itr.current())) {
    case e_pttransform:
      // Get transform matrix for this element. Unlike path.GetCTM()
      // that return full transformation matrix gs.GetTransform() return
      // only the transformation matrix that was installed for this element.
      //
      // gs.getTransform()
      break
    case e_ptline_width:
      // gs.getLineWidth()
      break
    case e_ptline_cap:
      // gs.getLineCap()
      break
    case e_ptline_join:
      // gs.getLineJoin()
      break
    case e_ptmiter_limit:
      // gs.GetmiterLimit()
      break
    case e_ptdash_pattern:
      // let dashes: NSMutableArray = gs.getDashes()
      // gs.getPhase()
      break
    default:
        break
  }
    gs_itr.next()
}
```

{% endcode %}
{% endtab %}
{% endtabs %}

[PDF Data Extraction (Images, Text, Paths)](/ios/get-started/samples.md#elementreaderadv) Full code sample which illustrates how to extract data, do color conversion, image normalization, and how to process changes in the graphics state.

## About graphics state

After reading an Element using `ElementReader.Next()`, it is possible to access all graphical attributes of the Element through its graphics state. Some applications are more interested in *changes* in the graphics state than attribute values. For example, a transition from one Element to another may not involve changes in the graphics state. Or, perhaps, there may be changes only to a couple of attributes. In these cases, it isn't efficient to make memberwise comparisons between the old and current graphics states.

To make this easier and more efficient, Apryse SDK offers an API to enumerate the list of changes between subsequent Elements.

It's also possible to query ElementReader for changes to a specific attribute:

{% tabs %}
{% tab title="Obj-C" %}
{% code lineNumbers="true" %}

```objc
if ([reader IsChanged:e_ptline_width])
{
   // line width was changed.
}
```

{% endcode %}
{% endtab %}

{% tab title="Swift" %}
{% code lineNumbers="true" %}

```swift
if (reader.isChanged(e_ptline_width))
{
   // line width was changed.
}
```

{% endcode %}
{% endtab %}
{% endtabs %}

Note that the list of modified attributes is accumulated when calling `ElementReader.Next()`. To clear the list of modified attributes use `ElementReader.ClearChangeList()` method. A call to `ClearChangeList()` serves as a marker in the display list from which further changes in the graphics state are tracked.


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