Rectangle Construction and Positioning in IronPDF

Curtis Chau

Updated: July 21, 2026

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  # Rectangle Construction and Positioning in IronPDF When you draw rectangles in a PDF with IronPDF, the coordinate system differs from libraries like IronOCR and IronBarcode. IronOCR and IronBarcode define rectangles relative to an image input, while IronPDF works within the coordinate space of the PDF document itself. ## Coordinate Origin The origin point `(0, 0)` sits at the **bottom-left corner** of the page. When you specify a rectangle, that origin is treated as the rectangle's **top-left corner**, which determines the direction the shape is drawn. ## Axis Behavior How the `x` and `y` values shift the rectangle: - **Y-coordinate:** increasing `y` moves the rectangle up; decreasing it moves the rectangle down. A negative `y` places the rectangle below the `(0, 0)` point. - **X-coordinate:** increasing `x` moves the rectangle to the right. Decreasing `x`, or supplying a negative value, shifts it to the left. ## Width and Height Dimensions can be drawn in either direction from the starting point: - **Width:** a positive `width` draws to the right; a negative or decreasing `width` draws to the left. - **Height:** a positive `height` extends upward; a negative `height` draws downward.  ## Unit of Measurement IronPDF measures its drawing API in **points**, giving the precision needed for document rendering and layout. The other Iron Software libraries differ: - **IronOCR:** uses **pixels** exclusively, matching its focus on image-based text recognition. - **IronBarcode:** uses **pixels** to locate barcode objects, but switches to **points** when stamping barcodes into a PDF so placement stays accurate in document formats. [[i:(Mixing units across libraries is a common source of misplaced shapes; confirm whether the API you are calling expects points or pixels.)]]

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When you draw rectangles in a PDF with IronPDF, the coordinate system differs from libraries like IronOCR and IronBarcode. IronOCR and IronBarcode define rectangles relative to an image input, while IronPDF works within the coordinate space of the PDF document itself.

Coordinate Origin

The origin point (0, 0) sits at the bottom-left corner of the page. When you specify a rectangle, that origin is treated as the rectangle's top-left corner, which determines the direction the shape is drawn.

Axis Behavior

How the x and y values shift the rectangle:

• Y-coordinate: increasing y moves the rectangle up; decreasing it moves the rectangle down. A negative y places the rectangle below the (0, 0) point.
• X-coordinate: increasing x moves the rectangle to the right. Decreasing x, or supplying a negative value, shifts it to the left.

Width and Height

Dimensions can be drawn in either direction from the starting point:

• Width: a positive width draws to the right; a negative or decreasing width draws to the left.
• Height: a positive height extends upward; a negative height draws downward.

Unit of Measurement

IronPDF measures its drawing API in points, giving the precision needed for document rendering and layout. The other Iron Software libraries differ:

• IronOCR: uses pixels exclusively, matching its focus on image-based text recognition.
• IronBarcode: uses pixels to locate barcode objects, but switches to points when stamping barcodes into a PDF so placement stays accurate in document formats.

Curtis Chau

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Technical Writer

Curtis Chau holds a Bachelor’s degree in Computer Science (Carleton University) and specializes in front-end development with expertise in Node.js, TypeScript, JavaScript, and React. Passionate about crafting intuitive and aesthetically pleasing user interfaces, Curtis enjoys working with modern frameworks and creating well-structured, visually appealing manuals.

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