Pursuing the "perfect" film dot repair technology
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The originals of the netted film are scanned and inserted into the layout and then printed out. This is used in the early stage of prepress digitalization for the remote transmission of newspaper layouts. Now, when CTP gradually replaces traditional platemaking, this technology is becoming more important and will become The key to the success of the digital version. The key to the digitization process of the net manuscript is the real restoration of the dot. The closer the dot is restored to the original, the more the technology can replace the traditional optical plate making process, and the more the computer direct plate making can represent its practicability. However, the true restoration of the net manuscript, in addition to the selection of a dedicated scanner and its mature use of COPYDOT technology, is another important point is the performance of the anti-dirty repair of the net film. The early "dirty" work was usually handled by a simple image processing system, and the general image processing software usually lacked the professional processing of the dot processing of the hanging film, often making the "dirty" function stay in the ordinary " On the level of "point processing", the repair of the dot, especially the processing of color four-color film, is often helpless. Recently, the “Fracture Professional Software” (Perfectin) launched by Escofut in Denmark is a professional image processing software for film scanning. Its appearance has undoubtedly brought new impetus to the current practical application of CTP.
"Fine-cleaning professional software" is a new feature that is different
The design of "Perfectly Repairing Professional Software" is designed for the characteristics of scanned dot images. The best format for hanging film scanning is basically positioned in the "bitmap" format of the image due to its special expression, "dirty" The processing is based on this format. When the film reflects the four-color image, the synthesis of the “four-color bitmap” shows the great advantage of this software. We have used image processing software engineers from the past. Photoshop describes the unusual aspects of this software in the same way as the comparison of dot processing methods.
(1) Restore the real network points, supplemented by a variety of decontamination functions, and fully realize the digital purification effect of the original network.
When ordinary image processing software uses its own "filter" (such as photoshop's filter filter) to identify "dirty dots" ("zao"), the range of values of "dirty dots" is usually selected and cannot be too large. Otherwise, the small dots are mistakenly judged as "dirty dots" and are filtered out to make the finished product appear "out of the net" phenomenon; and the "dirty spots" appearing in the blank area need to be selected by region, cleaned by region, with low efficiency; as for the outlets The "dirty spots" in the middle are difficult to identify and remove due to the adhesion with the dots. For example, the manual repair is performed in the form of pixels. The workload is huge, and the shape of the repaired dots is different, which directly affects the quality of the film original on the finished product.
"Perfect" (Perfect) provides four kinds of filter tools based on the shape of the film AM, the number of screen lines, the angle of the screen, etc., based on the filter used by the general image processing software. :Autoclean, dustfllter, Dotclean, Rexample, with the net network compensation calculation to achieve the perfect simulation of the mesh simulation of the processed original. Among them, "Dotclean" is a system automatic analysis for "dirty dots" between "spots", removing black spots that are not outside the "spots", and can give edge rounding correction according to the "mesh" shape.
The correction also considers the transitional change of the "mesh" that represents the "gray change". Therefore, the design of this function is like "finishing the finishing touch" for the whole "dirty" work, which becomes the key to digital purification of the net original. With the help of other filters, it is a breeze to get dirty at the outlet.
(2) Adopting novel processing methods to break through the limitations of the standard picture format, so that the “dirty” function is truly efficient.
Film scanning must use high-resolution "bitmap" input to have higher dot reduction characteristics. We have already explained this through many experiments and special discussions. Therefore, all image processing software that calls such large resolution graphics Faced with the speed and efficiency of the process, PhotoShop is no exception. When the film is color content, the four large-capacity "bitmaps" reflecting the four colors are simultaneously processed, which causes problems for ordinary image processing software such as Photoshop.
On the one hand, the image format is not targeted to the format of a color image consisting of four-color "channels" that are both "bitmaps", because the standard multi-channel color image must have a "grayscale" for each color format, in order to process When "dirty" is convenient to display, it is necessary to convert the format of each "bitmap" into the format of "grayscale". This is the process, and the image conversion footprint is increased after being converted into "grayscale". 8 times to the "bitmap"! Taking 8 open film as an example, when scanning at 900 dpi, the color separation "bitmap" file size is 12.5 megabytes/color, and after converting to "grayscale image", the file is sharply increased to 100 megabytes/color, and the synthesized four-color file is Up to 400 megabytes. Such a high capacity requirement has high requirements for the computer for processing pictures, such as memory and central processing unit. In actual use, we have encountered the phenomenon of "dead" caused by excessive space occupied by pictures. Therefore, the conventional image processing software has a problem of "too low efficiency" in processing a film scan picture.
On the other hand, after the ordinary image processing software performs the smear in the color mode of the color film, it also needs to return to the "bitmap" to provide the layout insertion output, which needs to go through the "bitmap" - "grayscale map" - "bitmap". Two conversions result in pixel loss, especially for high-light partial dots. However, the direct use of CMYK's TIFF format instead of the second conversion makes the file too large, the illuminating time is prolonged, and the secondary hanging nets performed according to the arrangement are likely to lose detail and moiré.
"Perfection" shows the level of professional film scanning purification. The software processes the color film image directly on the "bitmap" of each color, and on the screen, it is synthesized in the form of "simulation", so that the "dirty" process can be performed without increasing the file capacity. It is fast and saves space. At the same time, after the repair of the dot is completed, the disk quality is saved without any loss. It completely breaks through the limitation of the standard image format, which is a breakthrough in the film decontamination technology.
Parameter setting of "dirty" software and its actual effect
"Perfection" makes the digitalization process of film simple and successful, which undoubtedly brings confidence to the current CTP to be practical. We repeatedly debugged the large-format scanner ESCOSCAN1724 to scan the film "dirty", and gained a little practical experience, and thought that the key to the "dirty" technology is to adapt to different conditions of film cleanness and dot pattern, call different filters And adjust the parameters to get the best results. Below we will give an introduction from the different performance and parameter settings of each filter.
(1) Features of Autoclean filter and its parameter settings. Mainly used for the removal of visceral points in a blank background.
The "radius" parameter determines the size of the dirty point to be removed. The appropriate value is 3-4 and the maximum is 6. When the size of the text is significantly larger than the size of the dirty point, the loss of pixels in the text is minimal;
"Threshold": 1% to 100% of the range of values, preferably set to 50%, when the black pixel value is greater than 50% will produce more black pixels, the effect is expressed as the final text thickening, dot When the scale is less than 50%, the opposite is true.
(2) Characteristics of the dustfilter filter and its parameter settings. The main use of text visceral point removal is more detailed than Autoclean's detailed parameter settings. The biggest advantage is that the removal of dirty spots also ensures the restoration of dot shape and size.
The “radius” parameter takes a value of 1–10. Generally, the value should be set lower, but it is larger than the radius of the dirty point. The effect of the avoidance filter is too heavy, causing the mesh to be damaged.
“Interactive Threshold”: When this item is selected, the lower/lower threshold will turn white below, the high threshold will turn black, but the inter-area dot value will remain unchanged;
"Recover Point Shape": It is used to reconstruct the data that you do not want to delete during the filter processing. This function checks which data is modified by comparing the data of the filter area. Once the black pixel is found to be adjacent, there is near black. Pixels, then the black pixels are expanded to reconstruct, such as dot edges, text outlines, and so on. Since the dustfilter filter operates at the level of the pixel, the filter settings should refer to the scan resolution and number of screen lines, the dot size and the number of pixels per dot.
(3) Features of Dotclean filter and its parameter settings. This filter is the core technology of the whole trimming software. It mainly removes the dirty spots in the AM screen and performs the dot recovery according to the shape and size of the dot. The parameter setting should be based on the resolution used in the scanning. Make adjustments.
“Size” parameter: It is related to the size of the dirty spot. It should be slightly larger than the radius of the dirty spot. The time required for the filter processing is proportional to the “size”. The larger the size, the longer the processing time, and the general dirty point is 5-10 seconds. Big may take 50 seconds;
"Effect": A relative value of the degree of filter effect control.
“Recover Point Shape”: This is a key parameter setting. When the film is scanned using the built-in Moire filter and its value is 0, Dotclean will rebuild the Moire you removed during scanning. Effect; when the large dirty spots in the dot area are to be removed, this value is 0;
"Restricted area": When this item is selected, Dotclean will not consider the network points outside the selection area when analyzing Dotclean;
“High-precision reproduction”: When selected, the “dirty” software analyzes 4 pixels with the default settings to obtain higher precision, which is dedicated to dot reproduction in low dot percentage areas, such as when each dot is only a few At the time of pixels, the filter processing time will be lengthened.
(4) The characteristics of the Rexample filter and its parameter settings. This filter is used to change the output size of the scanned image, which can be a change in length or width, or scaled proportionally. This technology is less practical, because the film scanning faithful original large hanging net density is not suitable to change its proportion, to prevent the deformation of the dot or the distance between the number of meshes of the full-end back-hanging net, and also prevent the turtle generated during the photo-alignment Patterns such as lines or nets.
Of course, "Perfection" is still being perfected and adjusted. In the process of use, attention should be paid to its shortcomings. For example, Dotclean cannot be used for dirty text or lines, especially in processing outlets. In the place with text, the text should be circled, otherwise the text will be misinterpreted as dirty and processed to produce text distortion or text plus white net. In spite of this, the "perfect repairing professional software" has been matured in the relevant processing of the film scanning due to the excellent performance of its professional technology. The quality of the digital processing of the net film into the full-page output is reliably guaranteed. The convergence of a technology fills the gaps in the CTP field, which has a far-reaching impact on the overall practicality of CTP.