Fig. 2

The ECG data input format. a The red-grid background of the 12-lead ECG image was removed and ECG was converted to a gray-scale image. b The pixel intensity was inversed and the pixel intensity was made to 255 pixels. The image was cut vertically into four sub-images according to the “start” and “end” position of each lead. c Pixel-wise scanning sub-images and recording the position where the pixel intensity was equal to 255 pixels. d The closest position of the signal was grouped. Each column was split into four values and all values of the columns were synthesized into four lists in each lead. The signals were transferred to be the time-series formats. e The column of each sub-image consisted of 250 pixels. After pixel-wise scanning, one lead with 250 time-series data was formatted. The interpolation operations were used to perform up-sampling for the time-series data (500 Hz, 2.5 s). f The IIR low-pass filter was used to filtered the noise (cut-off frequency = 15 Hz, order = 3). g The magnitude of each lead was normalized into a unified scale