正方体错误：警告。无效的分辨率 0 dpi。改用 70

Question

在图片上运行tesseract时报错（附图）

tesseract rsa-out.jpg stdout

Warning. Invalid resolution 0 dpi. Using 70 instead.
Empty page!!
Empty page!!

Answer 1

图像的元数据可能不包括图像分辨率。如果您知道，您可以使用--dpi 命令选项为输入图像指定 DPI。运行tesseract --help-extra 以获取更多信息。

已更新版本信息和 cmd 输出：

>tesseract -v
tesseract 4.1.1
 leptonica-1.79.0 (Jan  2 2020, 22:29:02) [MSC v.1924 DLL Release x64]
  libgif 5.1.4 : libjpeg 9c : libpng 1.6.37 : libtiff 4.0.10 : zlib 1.2.11 : libwebp 1.0.3 : libopenjp2 2.3.1

>tesseract --help-extra
Usage:
  tesseract --help | --help-extra | --help-psm | --help-oem | --version
  tesseract --list-langs [--tessdata-dir PATH]
  tesseract --print-parameters [options...] [configfile...]
  tesseract imagename|imagelist|stdin outputbase|stdout [options...] [configfile...]

OCR options:
  --tessdata-dir PATH   Specify the location of tessdata path.
  --user-words PATH     Specify the location of user words file.
  --user-patterns PATH  Specify the location of user patterns file.
  --dpi VALUE           Specify DPI for input image.
  -l LANG[+LANG]        Specify language(s) used for OCR.
  -c VAR=VALUE          Set value for config variables.
                        Multiple -c arguments are allowed.
  --psm NUM             Specify page segmentation mode.
  --oem NUM             Specify OCR Engine mode.
NOTE: These options must occur before any configfile.

Page segmentation modes:
  0    Orientation and script detection (OSD) only.
  1    Automatic page segmentation with OSD.
  2    Automatic page segmentation, but no OSD, or OCR. (not implemented)
  3    Fully automatic page segmentation, but no OSD. (Default)
  4    Assume a single column of text of variable sizes.
  5    Assume a single uniform block of vertically aligned text.
  6    Assume a single uniform block of text.
  7    Treat the image as a single text line.
  8    Treat the image as a single word.
  9    Treat the image as a single word in a circle.
 10    Treat the image as a single character.
 11    Sparse text. Find as much text as possible in no particular order.
 12    Sparse text with OSD.
 13    Raw line. Treat the image as a single text line,
       bypassing hacks that are Tesseract-specific.

OCR Engine modes:
  0    Legacy engine only.
  1    Neural nets LSTM engine only.
  2    Legacy + LSTM engines.
  3    Default, based on what is available.

Single options:
  -h, --help            Show minimal help message.
  --help-extra          Show extra help for advanced users.
  --help-psm            Show page segmentation modes.
  --help-oem            Show OCR Engine modes.
  -v, --version         Show version information.
  --list-langs          List available languages for tesseract engine.
  --print-parameters    Print tesseract parameters.

Answer 2

警告告诉您输入图像的元数据中不包含分辨率信息，因此 Tesseract 会发出警告，然后尝试自行估计分辨率。 您可以参考此issue 了解更多信息。

Answer 3

要测试图像是否具有正确的标题，您可以使用 magick identify -verbose 文件名或等效工具

并确保设置了这两个值 分辨率：118.11x118.11 单位：像素每厘米 以上是 300 dpi PNG

Answer 4

您应该能够使用以下行正常加载它：

import cv2
import pytesseract

image = cv2.imread('FS313.jpg')
text = pytesseract.image_to_string(image,lang='eng',config='--psm 3') 

但是，无论 psm 如何，您都无法获得准确的 OCR 结果，因为 Tesseract 没有针对此类数字进行训练。如果您愿意，有一个视频可以帮助您自己训练它，名为“Tesseract OCR - 为七段创建训练数据（示例）”。

Answer 5

public class Test {
    public static void main(String[] args) {
        File imageFile = new File("C:\\Users\\data.jpg");
        ITesseract instance = new Tesseract(); 
        
        instance.setTessVariable("user_defined_dpi", "96");
         System.err.println(instance.getClass().getName().toString());
        try {
            String result = instance.doOCR(imageFile);
            System.out.println(result);
        } catch (TesseractException e) {
            System.err.println(e.getMessage());
        }
    }
}

添加这一行：instance.setTessVariable("user_defined_dpi", "96");