To vectorize a bitmap with Inkscape, you will first need to trace the lines in the image. The application offers an automatic plotting tool that does not require special drawing skills. You can also opt to manually use the software's built-in drawing tools if you want to control your paths with more precision. No matter which method you choose, vectorizing your bitmap images will be made easy with this free and open source software, which is available for Windows, Mac, and Linux.
Method 1 of 2: Automatically trace
Step 1. Import a bitmap image
Click on File in the top menu bar of the application, then select the option Import. Choose the image to vectorize in the dialog that will appear.
Step 2. Open the plot tool
Click on Path in the top menu bar, then select Vectorize the bitmap. A dialog window will appear, offering you to adjust various vectorization parameters.
Step 3. Choose the number of tracing passes to perform
Adjust the settings at the top of the dialog, titled Simple Pass, if you want to create a single path from the image. Adjust the ones in the lower part, titled Multiple passes, if you want to obtain several overlapping paths.
- You will need to adjust a few settings to vectorize your bitmap image in a single pass.
- The setting of Brightness threshold will use a pixel's shading to determine whether it should be white or black in the plot. The higher the value of this parameter, the thicker the output path will be.
- The adjustment of the Contour detection will determine the plot based on the color differences of the pixels. The detection level settings will affect the thickness of the output traces, in the same way as for the brightness threshold setting.
- The parameter Color quantization will produce a plot based on the differences between the colors. The Number of Colors setting will give you the opportunity to specify the number of colors to use if the output can be determined based on those of the bitmap. A special algorithm is used to convert these theoretical colors to black or white and generate the plot.
- You will need to adjust a few additional parameters to obtain multiple scribing passes.
- Adjustment Brightness levels will allow you to specify the total number of passes to be made.
- Adjustment Colors will use the number selected in the box named Passes to determine how many colors should be supported to generate the output plots. This setting will only be effective if the bitmap image is in color.
- The parameter Shades of grey will act in the same way as the colors, but will affect the gray scale levels of the bitmap image. This adjustment will be effective if this image is in grayscale mode rather than in color.
- Among the additional options, Soften will apply a Gaussian blur to the bitmap image before it is vectorized and Stack the passes will fill in the blanks due to the indecision remaining in the covering of the paths. Check the option Remove background to remove it from the bitmap image, it usually consists of very light colors and should not have any influence on the path of the main subject.
- Click on the tab titled Options of the vectorization dialog.
- The option Remove parasites will remove unwanted dots and scratches that may exist on your bitmap if it has been scanned.
- Optimize paths will round the open angles of the paths in the form of Bézier curves. Likewise, the option Soften the corners will transform the acute angles into roundings of small radius.
Step 4. Preview your vectorized image
Click Update to display the result of your vectorization. If the lines seem too thick or are barely visible, you may have chosen a drawing method that is not suitable for your bitmap image. Inkscape recommends that you run a minimum of three trials with different settings to help you determine which of the results you get is the best plot for your needs.
Step 5. Create the plots and save your work
Click on the Validate button located in the lower right part of the vectorization dialog. The bitmap image will be saved in the resulting.SVG file.
Step 6. Edit and refine your results
Click on the second icon from the top of the toolbar on the left of your screen. You can also press the F2 key to adjust the curves by moving the nodes placed on the path as needed.
Method 2 of 2: Do a manual tracing
Step 1. Upload your image
Click on File in the menu bar, then select Import.
Step 2. Open the layer creation dialog
While tracing on a new layer is only technically optional, it will help you understand what you are doing by giving you the flexibility to vary the opacity settings on the layer you will be using for vectorization of your bitmap. Click Layer in the main menu bar, then select the option Layers located at the bottom of the drop-down menu.
Step 3. Add a new layer
Click the + button at the top of the layers bar on the right of your screen. Enter a name for the new layer (choose for example Plotter), click the Add button and position it in the foreground by clicking on the arrow pointing up and surmounted by a horizontal bar.
Step 4. Select a plotting tool
There are several in Inkscape, all of which meet different needs.
- Press the F6 key on your keyboard or click on the pencil icon in the toolbar to select the freehand drawing tool. It will allow you to draw paths anywhere in your image. If you only have a few plots to make, if you have a steady hand or if you have a graphics tablet, this tool will be more than enough for you.
- Simultaneously press Shift + F6 or click on the fountain pen icon to open the Bézier curve tool. This will allow you to cut your lines into several small segments that you can move and bend individually. If you are using a mouse and have multiple lines to draw, this tool will give you the most accurate results. You will need to double-click at the end of each line to complete the path and cut it into segments that will be editable.
Step 5. Draw all the lines in your image
Use your mouse or graphics tablet to do this. If you are using the Bézier curve plotter, try to draw short lines. They will be easier to edit than long lines, you can give them more precision and you will not have to redo the entire route in case of difficulty.
- You can switch from one drawing layer to another using the layer management box. All you have to do is double-click on the name of the one you want to work on and you will immediately be taken to it.
- Changing the opacity of your bitmap may help you while drawing your lines. You can adjust it to your liking using the slider located in the layer management box, just below the name of the layer.
Step 6. Open the node editing tool
Click on the second icon from the top of the toolbar on the left of your screen. You can also press the F2 key. This will allow you to click and drag the nodes that are positioned on your lines to adjust them.
If the number of nodes is too large and it takes forever to edit them, you can simplify them. The shape you draw will only be affected slightly, and it will be barely noticeable if you proceed wisely. Press Ctrl + L (or ⌘ Cmd + L on a Mac) to reduce the number of segments in your path
Step 7. Check the appearance of your plot without the bitmap
In order to make sure that you have vectorized all the lines of the bitmap that you are interested in, click on the first layer (the one that supports the original bitmap image) and increase its transparency using the slider named Opacity until it becomes invisible and you can only see your tracks. If you find that you forgot one, increase the opacity of your bitmap image again so that the lines you need to draw are visible again.
Step 8. Delete the layer supporting the bitmap image
Click on the first layer (the one supporting your bitmap) and delete it by clicking the - icon in the layer management box. Then save your track by clicking on File in the top menu bar then by choosing the option Save as. Don't forget to give your vector drawing a name.
- You will improve the quality of your paths by removing the background from the bitmap image before proceeding with the vectorization. Experts recommend using SIOX to remove the background from your bitmap image before you start plotting.
- Bitmaps with a high number of colors and large gradients will require more precision than the Auto Vectorizer can provide.