Image processing device

1. An image processing device, comprising:

first means for distinguishing first type images specified by two levels from second type images specified by other levels different from the two levels in accordance with first information related to image concentrations in image information, including letter distinguishing means for distinguishing the letter-like images as the first type images from the picture-like images as the second type images by comparing a maximum-minimum image concentration difference of the image information with a predetermined reference image concentration;

second means for distinguishing the second type images into letter-like images and picture-like images in accordance with second information related to the image concentrations in the image information, including:

bold letter distinguishing means for distinguishing the picture-like images into bold letter-like images and non-bold letter-like images by comparing a mean image concentration of the images with a predetermined reference mean image concentration;

means for smoothing the non-bold letter-like images;

means for accentuating edges of the images smoothed by the smoothing means; and

means for normalizing the maximum-minimum image concentration difference of the images accentuated by the accentuating means with respect to a predetermined mean image concentration; and

means for processing the images in accordance with distinctions among the images, made by the first and second distinguishing means.

2. The device of claim 1, wherein the second distinguishing means also includes poorly contrasted letter distinguishing means for distinguishing the picture-like images into poorly contrasted letter-like images and non-poorly contrasted letter-like images by comparing the maximum-minimum image concentration difference normalized by the normalizing means with a predetermined reference image concentration.

3. An image processing device, comprising: means for detecting maximum and minimum values of information related to image concentrations in image information;

means for calculating a normalized value from the maximum and minimum values, including means for normalizing one of the maximum and minimum values of the information related to the image concentrations with respect to the other of the maximum and minimum values;

difference calculating means for calculating differences in the information related to image concentrations between neighboring picture elements, including:

means for smoothing the images of the information;

means for accentuating edges of the images smoothed by the smoothing means; and

means for deriving maximum and minimum concentration differences of the image concentrations of neighboring picture elements from the accentuated images;

second detecting means for detecting maximum and minimum values of the differences between neighboring picture elements;

means for distinguishing letter-like images from picture-like images by comparing the normalized value with a predetermined reference value; and

means for processing the images in accordance with a distinction among the images, made by the distinguishing means.

4. The device of claim 3, wherein the detecting means includes means for detecting a maximum and minimum image concentrations of the image information as the maximum and minimum values, respectively.

5. The device of claim 3, wherein the distinguishing means includes letter distinguishing means for distinguishing the letter-like images from the picture-like images by comparing the normalized value with a predetermined reference value.

6. The device of claim 3, wherein the processing means includes:

first means for generating a binarization threshold for the letter-like images;

second means for generating a binarization threshold for the picture-like images;

means for selecting one of the first and second binarization thresholds in accordance with the selection of the one of the letter-like images and the picture-like images; and

means for comparing the selected one binarization threshold with the image information.

7. The device of claim 3, wherein the calculating means includes means for calculating the normalized value as a difference between the maximum and minimum values normalized with respect to a mean of the maximum and minimum values.

8. The device of claim 7, wherein the detecting means includes means for detecting the maximum and minimum image concentrations of the image information as the maximum and minimum values, respectively.

9. The device of claim 7, wherein the distinguishing means includes letter distinguishing means for distinguishing the letter-like images from the picture-like images by comparing the normalized value with a predetermined reference value.

10. The device of claim 9, wherein the processing means includes:

first means for generating a first binarization threshold for letter-like images;

second means for generating a second binarization threshold for picture-like images;

means for selecting one of the first and second binarization thresholds in accordance with the selection of one of the letter-like images and the picture-like images; and

means for comparing the selected one binarization threshold with the image information.

11. An image processing device, comprising:

difference calculating means for calculating a difference between maximum and minimum values of changes in information related to the image concentrations in image information, including:

means for smoothing the images of the image information; and

means for accentuating edges of the images smoothed by the smoothing means;

distance calculating means for calculating a distance between points in the image at which the changes in the information reach the maximum and minimum values;

ratio calculating means for calculating a ratio of the difference calculated by the difference calculating means and the distance calculated by the distance calculating means;

means for distinguishing letter-like images from picture-like images by comparing the ratio calculated by the ratio calculating means and a predetermined reference value; and

means for processing images in accordance with a distinction among the images, made by the distinguishing means.

12. The device of claim 11, wherein the difference calculating means also includes means for deriving a maximum concentration difference in the accentuated images between points at which the Laplacian operated images corresponding to edges reach the maximum and minimum values.

13. The device of claim 11, wherein the distance calculating means includes:

means for smoothing the images of the image information; and

means for accentuating edges of the images smoothed by the smoothing means.

14. The device of claim 13, wherein the distance calculating means also includes means for deriving a distance in the accentuated images between points at which the Laplacian operated images corresponding to edges reach the maximum and minimum values.

15. An image processing device, comprising:

first calculating means for calculating a square sum average of differences in an information related to image concentrations in image information between neighboring picture elements, including:

means for smoothing the images of the image information; and

means for accentuating edges of the images smoothed by the smoothing means;

second calculating means for calculating a mean value of the information related to the image concentrations;

third calculating means for calculating a normalized value as the square sum average normalized with respect to the mean value;

means for distinguishing letter-like images from picture-like images by comparing the normalized value with a predetermined reference value; and

means for processing images in accordance with a distinction among the images, made by the distinguishing means.

16. The device of claim 15, wherein the first calculating means also includes means for deriving the square sum average of concentration differences of neighboring images from the accentuated images of the image information.