FR2699777A1 - Facsimile transmission with variable resolution according to image - Google Patents

Abstract

The image data on a page is divided, into a certain number of surfaces. A counter (7) counts the number of changes between black and white in a given surface. A comparator (13) compares stored reference values (14) with the number of changes in contrast in the data and decides upon the resolution according to whether a certain threshold is exceeded. The document is read (1), analogue processed (2) and binary coded (3) for storing image data in a memory (4) such that the lines of the image of the document correspond to lines of stored image data. An address generator (10), taking valves from X and Y counters (7, 9), causes a buffer memory (5) to hold line data of a prescribed address for counting.

Description

 The present invention relates to a facsimile machine which automatically selects an optimal resolution in a subsidiary exploration direction.

 When using a conventional facsimile machine to read a document, an operator selects a reproduction quality mode (scanning line density mode) before reading the document. More particularly, if the image on the document is large and simple, the operator generally selects a standard mode (normal mode). On the other hand, if the image on the document is fine and / or complicated, the operator chooses a good quality mode (fine mode) and if the image is finer and more complicated, the operator chooses a mode very good quality (superfine mode).

 In a conventional facsimile machine, the resolution in a subsidiary scanning direction is generally set at 3.85 lines / mm when selecting the normal mode. When selecting the fine mode, the resolution in the subsidiary exploration direction is set to 7.7 lines / mm (twice the normal mode), and when the superfine mode is selected, the resolution is 15.4 lines / mm (double of fine mode).

 Traditionally, the operator judges the fineness of the image on the document and selects a quality of reproduction appropriate to the fineness of the image before transmitting the information on the document to a correspondent.

 However, as the sharpness of the image is subjectively judged by the operator, the selected mode may not be the best mode. If the most appropriate mode is not selected, the information transmitted cannot be understood on the receiver side. For example, if the image on the document is fine but the operator selects a normal mode, part of the information on the document may be refined too much by the data transmission process.

 Likewise, if the image of the document is large but the operator selects a fine or superfine mode, it takes a long period of time for the transmission of data in comparison with the case of a transmission in normal mode.

 The object of the present invention is to provide a facsimile machine which automatically selects the most suitable resolution so that the image data on the document is transmitted with sufficient clarity in a reasonable time.

 According to one aspect of the present invention, there is provided a facsimile machine comprising means for reading an image from a document, memory means for storing the letters read by the reading means in the form of image data (binary data black and white), means for counting the number of changes from white to black and / or vice versa in a predetermined area on the document using the image data in the memory means and means for determining the resolution in a subsidiary exploration direction for the image data according to a value counted by the counting means.

 According to this construction, the image on the document is read by the reading means. Then, the image is stored as image data. Then, the counting means counts the number of change points between white and black in the area prescribed on the document. Finally, the resolution determining means determines the linear density based on the value counted by the counting means.

The invention will be better understood and other objects, characteristics, details and advantages thereof will appear more clearly in the explanatory description which follows, made with reference to the appended schematic drawings given solely by way of example illustrating several embodiments of the invention and in which
- Figure 1 gives a block diagram of a facsimile machine according to an embodiment of the present invention
- Figure 2 (a) is an illustration of the image data of a document read by an image sensor
- Figure 2 (b) shows the image data in a first window after serial conversion
- Figure 2 (c) shows a time diagram of the clock pulses produced by a clock pulse generator
- Figure 2 (d) illustrates the line intervals for respective windows
- Figure 2 (e) shows the surface of the first window
- Figure 2 (f) shows the counted number of change points; and
- Figure 3 gives a block diagram of a facsimile machine according to another embodiment of the present invention.

 Preferred embodiments of the invention will now be described with reference to the accompanying drawings.

 Referring to FIG. 1, an image sensor 1, which serves as reading means, comprises a charge counting device or CCD. The image sensor 1 reads the image on a document and transmits read signals to an analog processing circuit 2. In this embodiment, the facsimile machine is always set in fine mode from the start. Consequently, the resolution in the direction of subsidiary exploration is always 7.7 lines / mm in the initial state. The analog processing circuit 2 processes the signals (shadow correction, gamma correction, etc.) transmitted by the image sensor 1 and applies the processed signals to a binary coding circuit 3. The binary coding circuit 3 codes the signals transmitted by the analog processing circuit 2 and applies them to an image memory 4 as image data. In other words, the binary coding circuit 3 converts the analog signals (as transmitted by the circuit 2) analog processing into digital signals.

 Furthermore, the binary coding circuit 3 transmits the same image data in parallel to a buffer memory 5 which serves as memory means, line by line (in the description which follows, the image data of a line will be called "line data"). Buffer 5 is a memory that can store line data in a predetermined amount (in this embodiment, buffer 5 can store line data on four lines).

 A clock signal generating circuit 6 produces a clock pulse and applies this pulse to an X-nary counter 7 and to a parallel-series converter (P / S converter) 8. The X-nary counter 7 performs the counting based on the clock pulse. The counting capacity of the X-meter 7 is seven in this embodiment. Consequently, the counter 7 will be reset when it has counted the clock pulse seven times. When the X-nary counter 7 is reset to zero, it applies a carry-over signal to the parallel-series converter circuit 8 and to a Y-nary counter 9 as well as a count value to an address generator circuit 10.

The counting capacity of counter 9 is four in this embodiment. The counter Y-nary 9 counts one on receipt of the signal to carry over from the counter X-nary 7 and it applies the count value to the address generating circuit 10. The counter Y-nary 9 will be reset when it has counted four times the transfer signal at the output of the X-nary counter 7. When reset, the counter
Y-naire 9 sends an "end of window signal" to a change point counter 11 and an AND circuit 12 (which will be described below). In other words, the X-counter 7 counts the number of picture elements in a main exploration direction and the Y-counter 9 counts the number of lines in a subsidiary exploration direction.

 The address generator circuit 10 applies an address signal to the buffer memory 5 based on the account value of the counter X-nary 7 and the account value of the counter Y-nary 9. The buffer memory 5 stores the line data at a prescribed address based on the address signal sent by the address signal generator circuit 10 and applies the line data to the parallel-to-serial converter 8.

 The address signal at the output of the buffer memory 5, coming from the address generator 10, is a signal which corresponds to the line data of 7 bits in a single line (one of the first to fourth lines). In this embodiment, a segment or area for the 7-bit line data in the first through fourth lines is called a "window" as shown in Figure 2 (a).

As can be seen in Figure 2 (a), the first window contains the row data for "L, H, H, L, L, L,
H "in the first line, the line data" H, H, L, L,
L, L, L "in the second row, the row data of" H,
H, H, L, L, H, H "in the third row and the row data of" L, L, L, H, L, H, H "in the fourth row.

 The buffer memory 5 transmits in succession, for the parallel-serial converter 8, the seven-bit line data in the first to fourth lines, which corresponds to the address signal at the output of the address generator 10.

The parallel-to-serial converter 8 receives in parallel at its input, from the buffer memory 8, the seven-bit line data in the first to fourth lines, based on the clock pulse of the generator 6 and the signal of transfer of the X-nary counter 7. More particularly, all the line data of a window are introduced in parallel into the parallel-series converter 8, line by line. Consequently, the "end of window signal" emitted by the counter Y-nary 9 is a signal which is emitted when all the line data of the fourth line of the window has been applied to the counter 11 of change points by the parallel-to-serial converter 8.

The parallel-serial converter 8 serially converts the line data of a window which has been introduced in parallel by the buffer memory 5 (see FIG. 2 (b)) and applies the line data to the counter 11 for change points, in the order of entry. Consequently, when the line data of the first window is transmitted to the change point counter 11, the "L" and "H" are arranged as follows and as shown in FIG. 2 (b):
H, H, L, L, L, H, H, H, L, L, L, L, L, H, H, H, L, L, H, H,
L, L, L, H, L, H, H.

 Whenever the change point counter 11 receives the window end signal from the Y-nary counter 9, that is to say when the transmission of line data from a window of the parallel-serial converter 8 is complete, as shown in Figures 2 (e) and 2 (f), the change point counter 11 has many change points (or turning points) in the row data for a window. As we now understand, the "change point" is a point where the transition from "H (black)" to "L (white)" occurs or vice versa. The change point counter 11 counts the number of these points. Therefore, as shown in Figures 2 (b) and 2 (f), the ENB change point count value from the first window is "11".

After counting the number of change points in the first window, the change point counter 11 applies the account value to a digital comparator 13.

 The digital comparator 13 compares the change point count value ENB coming from the change point counter 11 with a predetermined value of change points ENA coming from a reference value register 14. Then, if the real value ENB is more important than the reference value ENA (ENB> ENA), the digital comparator 13 transmits "H (high)" at its output terminal. On the other hand, if the real value ENB is less than or equal to the reference value ENA (ENB <ENA), the digital comparator 13 emits a signal "L (low)". It should be noted here that the reference value ENA which is stored in the register 14 has been determined by experience or the like.

If the actual ENB value exceeds the reference value
ENA, that is to say if the signal at the output of the digital comparator 13 is "H" this indicates that the number of change points is important. Consequently, we can deduce that the image in the window is fine and / or complicated.

 On the other hand, if the actual value ENB does not exceed the reference value ENA, that is to say if the signal at the output of the digital comparator 13 is "L", this indicates that the number of change points is small. Consequently, we can deduce that the image in the window is simple.

 For example, if the reference value ENA is "6", the signal at the output of the digital comparator 13 is "H" because the value of count of change point ENB is "11" as mentioned previously and as shown in Figure 2 (f). Therefore, we can judge that the image of the first window is fine and complicated.

 The judgment signal is then applied to a flip-flop or flip-flop circuit 15 by the digital comparator 13 and the circuit 15 stores the signal "H". After storage of the signal "H" in the flip-flop circuit 15, this signal "H" is inverted into "L" in a NON 16 circuit.

This inverted "L" signal is then transferred to an AND circuit 12.

Consequently, the end of window signal (flip-flop clock signal: F / F clock) is not added to circuit 15 via AND circuit 12. Consequently, even if the digital comparator 13 emits a signal " L ", this signal" L "is not introduced into the flip-flop circuit 15.

 After reading the document, a controller (not shown) emits an end-of-page signal for the flip-flop circuit 15 and a resolution change circuit 17 (means for determining linear density). On receipt of the end-of-page signal, the flip-flop circuit 15 is reset to its initial state and the judgment signal in circuit 15 is reset to "L". On receipt of the end of page signal, the resolution change circuit 17 changes the resolution for the line data stored in the image memory 4 to a normal mode and codes the line data in normal mode or maintains the resolution current (fine mode) and codes the line data in fine mode according to a final signal from circuit 15.

 More particularly, if the judgment signal of circuit 15 is "H", the resolution determination circuit 17 maintains the resolution for the image data in the image memory 4 in current mode (fine mode: 7.7 lines / mm) and codes the image data in a coding circuit 18.

On the other hand, if the judgment signal of the flip-flop circuit 15 is "L", the resolution determination circuit 17 changes the resolution to a normal mode (3.85 lines / mm), starting from the fine mode, and codes the image data in the coding circuit 18 in normal mode. The coded image data are applied to a communication line via a modem (modulator-demodulator) 19 by the coding circuit 18.

 The operation of the facsimile machine having the construction described above will now be explained.

 First, the image on the document is read by the image sensor 1 in fine mode. The image is then processed analogically and put in digital form. The signal in digital form is stored in the image memory 4 as well as in the buffer memory 5 in parallel. When the line data representing the quantity of four lines is entered into the buffer memory 5, the line data in this memory 5, specified by the address generator circuit 10, are sent to the parallel series converter 8, line by line. The line data is converted in series in the converter 8 and the number of change points between "H (black)" and "L (white)" is counted in the change point counter 11.

Then, while the end of window signal is applied to the parallel-series converter 8 by the counter
Y-nary 9, that is to say that the change point counter 11 finishes counting the number of change points for a window, the account value (ENB) is applied to the digital comparator 13 by the counter 11 change points. Simultaneously, the counter 11 begins to count the number of change points in a next window.

In the digital comparator 13, the predetermined reference value ENA supplied by the reference value register 14 is compared with the account value
ENB supplied by the change point counter 11. If the account value ENB is not greater than the reference value ENA, the digital comparator 13 applies a signal "L" to the flip-flop circuit 15.

 If a signal "H" is not emitted by the digital comparator 13 until the entry of the end-of-page signal and only the signals "L" are stored in the flip-flop circuit 15, the resolution for the image data in memory 4 is changed. More particularly, the resolution in the subsidiary exploration direction is converted to 3.85 lines / mm from 7.7 lines / mm and the image data in the memory 4 are coded in the coding circuit 8 at the exploration density of 3.85 lines / mm, then it is transmitted to a correspondent by the modulator-demodulator 19 and the transmission line. The resolution conversion can be undertaken by a simple thinning process or a processing OR or logical meeting. The logical meeting makes it possible to calculate the theoretical sum of corresponding image elements in two adjacent lines so as not to make these two lines only one line.

 On the other hand, if the digital comparator 13 transmits a signal "H", the resolution for the image data in the image memory 4 is not changed and the image data is coded in the coding circuit. 4 at the resolution of 7.7 lines / mm. Then, the coded image data are transmitted to the correspondent by the modem 19 and the communication line.

 According to the facsimile machine of this embodiment, as can be understood from the above, when the image data is stored in memory 4, the resolution in the subsidiary scanning direction is always 7.7 lines / mm (fine mode), at the start. Then, the image data is divided into two windows and the number of change points from white (L) to black (H) and vice versa, is counted for each window.

 If the ENB account value exceeds the ENA reference value, even once, before the counting of change points for all windows on a page is completed, this indicates that the document contains at least somewhere a complicated image . Consequently, the image data in the memory 4 are transmitted to the correspondent in initial mode (fine mode).

 On the other hand, if the ENB account value has never exceeded the ENA reference value at the time the counting of change points for all the windows of a page is completed, we can judge that the document does not contain no complicated picture. Consequently, the image data of the memory 4 is transmitted to the correspondent in a relatively coarse mode of 3.85 lines / mm (normal mode).

 In summary, in this embodiment, the image on the document is not judged by the sensitivity of the operator.

The fax machine divides the document into several areas to form the windows and judges the image on the document based on the number of change points in the windows, then the fax machine selects an optimal resolution for particular data d based on judgment. As a result, unlike the conventional facsimile machine, that of this embodiment can transmit the image data in an optimum time, which enables economical data transmission.

 A second embodiment of the present invention will now be explained with reference to FIG. 3. It should be noted that identical figures are assigned to identical elements in FIGS. 1 and 3, the explanation of such elements being omitted here.

 Also in this embodiment, the resolution in the direction of subsidiary exploration is initially established at 7.7 lines / mm (fine mode). After digitalization of the image data of the output of the analog processing circuit 2 in the binary coding circuit 3, this image data is applied to the image memory 4 as in the preceding embodiment. At the same time, the line data is applied in succession to first to y-th shift registers 21a-21y.

 Each of the shift registers 21a-21y stores the image data of a line (line data in a line in a main scanning direction). More particularly, the line data with a width of 7.7 lines / mm at the output of the binary coding circuit 3 are successively introduced into the first to y-th shift registers 21a-21y. Thus, when the line data is introduced into the last shift register 21y, a clock signal which specifies a first shift register 21a is applied to this first shift register 21a by a clock control circuit 22.

 On receipt of the clock signal from circuit 22, the first shift register 21a applies the line data to a data selector 23. The selector 23 applies the line data to the change point counter 11 based on the count value at the output of counter Ynaire 9. In counter 11, the number of change points between black and white is counted in the row data.

 When the X-nary counter 7 has finished counting, the circuit 22 increases the Y-nary counter 9 on reception of a signal to carry over from the X-nary counter 7, forces the data selector 23 to choose the output of the second shift register 21b and apply a clock signal to the second shift register 21b to shift it. Like the first shift register 21a, the second shift register 21b applies the line data to the data selector 23 upon receipt of the clock signal from the clock control circuit 22. Then, the line data is transmitted to the 11 change point counter by the data selector 23 for counting the change points between black and white.

 Next, the clock control circuit 22 transmits the clock signals in succession to specify the shift registers remaining up to the y-th shift register 21y, in the same way as the first and second registers have been specified. offset 21a and 2lob. The clock control circuit 22 is reset to its initial state when it has finished the output of the clock signals to the y-th shift register 21y and the circuit 22 repeats the same process from the first shift register 21a.

 Then, the line data of the y-th shift register 21y is input to the change point counter 11 by the data selector 23 to count the number of change points in the line data.

After counting the number of change points in the line data of the y-th shift register 21y, the counter 11 adds the numbers of the change points of the first to y-th shift registers 21a to 21y and transmits a count value of total change points ENB for the digital comparator 13.

 Then, the reference value ENA in the reference value register 14 is compared with the change point count value ENB provided by the change point counter 11 in the digital comparator 13 and the result of the comparison is applied to the flip-flop circuit 15.

Then, the processes are identical to those of the first embodiment, the explanation will therefore be omitted.

 Like the first embodiment, according to this embodiment, the image on the document is not judged by the operator but the fax machine itself judges the fineness and the complication of the image to determine a density. optimal linear for data transmission.

Consequently, the same technical advantages are obtained as in the first embodiment.

 Although the window includes seven picture elements in the main exploration direction and four lines in the subsidiary exploration direction in the first embodiment, the size of the window can be changed as desired. In the first and second embodiments, the facsimile machine selects normal mode (3.85 lines / mm) or fine mode (7.7 lines / mm) for transmitting image data using a single reference value. However, another reference value can be used to allow selection of the superfine mode. More particularly, the resolution in the subsidiary exploration direction may be 15.4 lines / mm, in certain cases.

 In the illustrated embodiments, the number of change points is counted as change from white to black and vice versa. However, it can only be counted when a change from white to black occurs or only when a change from black to white occurs.

Claims (11)

 1. Facsimile machine characterized in that it comprises  means for reading the image on a document (1);  memory means (4) for storing the image read by the reading means as image data;  means (7) for counting the number of changes from white to black and / or vice versa, within a predetermined area, on the document using the image data in the memory means; and  means (13) for determining the resolution in a subsidiary scanning direction for the image data according to a value counted by the counting means.  2. Machine according to claim 1, characterized in that the image data on a page of the document are divided into a certain number of surfaces, the counting means (7) counts in succession the number of changes between black and white for the respective surfaces, the resolution determining means (13) selects a relatively high resolution in the subsidiary exploration direction if a surface having a number of changes greater than a predetermined value is found.  3. Machine according to claim 1, characterized in that it further comprises a means (2) for the analog processing of the image as read by the reading means and a means (3) of binary coding to put the the image processed analogically in digital form and in that the binary coded letters are stored in memory means in the form of image data.  4. Machine according to claim 1, characterized in that the memory means comprises a buffer memory (5).  5. Machine according to claim 1, characterized in that the lines of the image on the document correspond to the lines of the image data in the memory means (4).  6. Machine according to claim 2, characterized in that it further comprises a memory of reference values (14) for storing the predetermined value.  7. Machine according to claim 6, characterized in that the relatively high resolution is the resolution of the fine mode.  8. Machine according to claim 2, characterized in that the means determining the resolution comprises a comparator (13) for finding a surface having a number of changes greater than the predetermined value.  9. Machine according to claim 1, characterized in that the lines of the image on the document correspond to lines of the image data stored in the memory means and in that the memory means comprises a certain number of registers shift (2la) to store, line by line, the image data.  10. Machine according to claim 1, characterized in that it further comprises a means for producing first and second reference values and in that the second reference value is greater than the first and the determining means (13) the resolution selects a fine mode if the value counted by the counting means is greater than the first reference value and selects a superfine mode if the value counted by the counting means is greater than the second reference value.  11. Machine according to claim 6, characterized in that it further comprises means for producing an address for reading the image data from the buffer memory and in that a certain area is captured from the stored image data. in the memory means using the address produced by the address generating means (10).