Image Processing Program

Background

After I was admitted to graduate school, my advisor gave me part of an image-processing industry project as practice. The project came from an outdoor poster company.

Problems

The main requirements were:

1. Generate PDFs from huge images.
2. Given a polygon and a spacing value d, generate a new polygon expanded outward by distance d.

Solutions

1. Generate PDFs from huge images

Study the PDF file format, and try either writing a PDF generation module by myself or using existing libraries such as libHaru or PDFWriter.

PDFWriter was used to implement cropping.

2. Generate an outward-offset polygon from a given polygon and spacing d

This is probably computational geometry. Since I had not studied it before, I first bought Computational Geometry: Algorithm Analysis and Design.

Edge-degeneration cases also need to be considered. References:

Polygon offset and fill algorithm

ClipperLib usage notes

3. A GUI may be needed for user friendliness

QT / Dear ImGui / wxWidgets

Notes

DPI means Dots Per Inch.

1 inch = 2.54 cm

100 DPI = 100 Dots Per Inch = 100 / 2.54 Dots Per Cm = 39.37 Dots Per Cm

Reference Links

Compiling and using LibHaru

Compiling libharu on Windows 10

Offsetting or shrinking polygons and contours by equal distance

Using wxWidgets binaries directly in Visual Studio 2019

wxWidgets wiki

Image processing: pixel-coordinate matrix transforms, including translation, rotation, scaling, and shearing

Determining whether a plane polygon is convex or concave