Bounding Box Guide

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What is a Bounding Box?

• Coordinates are expressed in points (pt).
• Size is expressed in points (pt).
• The origin of the document, or position (0,0), is located at the top-left corner.

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The Bounding Box Array

• x: The horizontal position of the first corner, measured from the left edge of the document.
• y: The vertical position of the first corner, measured from the top edge of the document.
• w: The width of the bounding box.
• h: The height of the bounding box.

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Bounding Box Example

{
  "boundingBox": [200, 300, 60, 40]
}

• The first corner of the field is located at 200 points from the left edge (x) and 300 points from the top edge (y) of the document.
• The field’s box has a width of 60 pt and a height of 40 pt.

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How can I find coordinates in my document?

Nitro PDF - Windows

Nitro PDF is available for Windows. You can download it in the user portal.

1

Open a document

Open a PDF document with Nitro PDF.

2

Set Points as measuring unit

Make sure the measuring unit in Nitro PDF is set to Points. To do this:

• Go to File tab in the navigation menu and select Preferences in the left panel. A preferences window will open.

• In the Preferences window, select Units and Grid from the left panel.
• In the Units section, set Default Units to Points from the dropdown menu.
• Click Apply to save your changes.

3

Select Crop tool (add it if needed)

To measure the bounding box dimensions, use the Crop tool. If it is available in your tools menu, select it.

If the Crop tool is not available, you will need to add it:

• Go to the Home tab in the navigation menu.
• Click Add Tools or Customize Tools in the upper-right corner of the application. A customization window will appear.

• In the search bar, type Crop and click Search.
• Select Crop from the results and add it to your Favorite tools.
• Click OK. The Crop tool will now appear in your tools menu.
• Select the Crop tool to activate it.

4

Draw the field rectangle with the Crop tool

Using the Crop tool, draw a rectangle over the area of the document where you want the field to appear.

5

Get the coordinates of the first corner of the rectangle

When you draw a box with the Nitro PDF Crop tool, it will display a series of measurements.To obtain the first corner (x, y) of your rectangle:

• The left-side measurement corresponds to x.
  • Example: 228.2 pt
• The top-side measurement corresponds to y.
  • Example: 637.8 pt

6

Get the rectangle's size

Using the same measurements from the Crop tool.

• First, note the width measurement of the rectangle.
  • Example: w = 168.15 pt
• Next, note the height measurement of the rectangle.
  • Example: h = 35.27 pt

7

Define the bounding box array

Given the measurements from the example above, the bounding box array to use in the Create Field API call is:

Copy

  "boundingBox": [228.2, 637.8, 168.15, 35.27]

Nitro PDF - Mac OS

Nitro PDF is available for Mac OS. You can download it in the user portal.

1

Open a document

Open a PDF document with Nitro PDF.

2

Get the document's dimensions

The first step after opening the document is to click on the Inspector located in the top-right corner.In the floating window that appears, select the Document Information tab .Take note of the document dimensions shown under Page Size. In the example, the document size is 595.3 pt x 841.9 pt.

3

Click the Select Rectangle tool

Scroll to the top of the Nitro PDF window until the tool menu expands. Then, click on the Select Rectangle tool .

4

Draw the field rectangle with the Select Rectangle tool

Using the Select Rectangle tool, draw a rectangle over the area where you want the field to appear in the document.

5

Get the coordinates of the first corner of the rectangle

When you draw a box with the Nitro PDF Select Rectangle tool, it will display a series of measurements. The zoomed-in view below shows an example of these values.To obtain the first corner (x, y) of your rectangle:

• The left-side measurement corresponds to x.
  • Example: 204.7 pt
• The top-side measurement corresponds to y.
  • Example: 613.8 pt

6

Get the coordinates of the opposing corner

Using the same measurements from the Select Rectangle tool, we can calculate the size of the rectangle.

• First, note the right-side measurement of the rectangle. This is the distance from the rectangle to the right edge of the document.
  • Example: 217.8 pt
• Next, note the bottom-side measurement of the rectangle. This is the distance from the rectangle to the bottom edge of the document.
  • Example: 193.8 pt

Now, calculate the width and height:

• Formula for w: w = Document Width − Right-side distance - Left-Side distance
  • w = 595.3 pt − 217.8 pt - 204.7 pt
  • w = 172.8 pt
• Formula for h: h = Document Height − Bottom-side distance - Top-side distance
  • h = 841.9 pt − 193.8 pt - 613.8
  • h = 34.3 pt

Nitro PDF Pro displays the width and height along the inside edges of the rectangle, as long as the rectangle is large enough to show them.

7

Define the bounding box array

Given the measurements from the example above, the bounding box array to use in the Create Field API call is:

Copy

  "boundingBox": [204.7, 613.8, 172.8, 34.3]

Preview - Mac OS

Preview is the built-in image viewer for macOS that allows you to easily identify point coordinates.For this example, we’ll use Preview on macOS (Version 11, build 1069). Keep in mind that behavior may vary across different software versions.

1

Select the Crop tool

Open Preview and click the Info icon . In the floating menu, select the Crop tool .In the floating window:

• Select Points as the measuring unit from the dropdown.
• Note the document size displayed under Media Box.

2

Locate the upper-left corner of your field

Decide where in the document you want the field to be placed, then use the Crop tool to draw a box in that area.Next, go to Info → Crop window again.

• In the Selection section of the floating menu, note the top and left measurements. These values will serve as the starting coordinates of your field x, y.
• Note the Width and Height w, h

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Example:
x: **225.25**
y: **700.51**
w: **153.26**
h: **40.36**

3

Define the bounding box array

Use the measurements above to construct your bounding box array.The bounding box parameter will look like this:

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 "boundingBox": [225.25, 700.51, 153.26, 40.36]