Data Acquisition from Scanned Graphs and Pictures

Note: There may be incompatibility in the graphics viewer for 64 bit systems.

The data acquisition goal is to read a picture (.bmp, .jpg, etc) which has a function graph (which may have been scanned) and extract from this graph the coordinates of the points of the function. These are the instructions for properly using the tool:

  • The color of the function to be acquired should be different from the rest of the colors of the picture. This is very important because otherwise the software won’t distinguish the function points from the points it should ignore. If this is not the case, I suggest you use MSPaint or some other color edition software prior to data acquisition.

  • The graph should be a function. If not, only the uppermost points will be acquired.

To acquire data, follow these steps:

  1. Click menu Figura -> Importar… and load the picture;

  2. Make sure that the function color is different from the other colors present;

  3. If the image doesn’t need rotation correction, skip to step 4. Else, calculate the correction angle, write in the “Rotacionar imagem (graus):” textbox, and click button Rotacionar until the rotation is correct;

  4. Click button Coordenadas Iniciais…, specify the initial coordinate value [x y] and click the point in the picture that corresponds to these coordinates;

  5. Likewise, click Coordenadas Finais…, specify the coordinate and click the point in the image that corresponds to the final coordinates. Important: the tool acquires points in all vertical span of the graph, but its horizontal span is between the initial and final coordinates only;

  6. Select the graph color. Do so by clicking the button Cor do Gráfico and, after that, click in a point inside the picture that has the graph color, i.e., click in a point of the graph so the system can identify its color. Check if the selected color is the correct one by looking at the color beside the button Cor do Gráfico;

  7. Click button Adquirir and specify how many equally spaced points should be acquired from the picture;
  8. Click button Plotar Dados… to manipulate the data.

If the picture is too large, just scroll using the scroll bars.

Export Data to File

After data acquisition, these are the steps to export the data to a file:

1. Click button Plotar Dados…;
2. Go to Lista de Curvas and select Y = f(x) adquirido;
3. Click menu Exportar/Importar dados -> Exportar para arquivo and save the file;
4. The file is then saved with x values in first column and y values in the second column.

One thought on “Data Acquisition from Scanned Graphs and Pictures”

Leave a Reply

Your email address will not be published. Required fields are marked *