Trapping in QM DI46-4

In the printing process, the high-speed transfer of the paper will produce a slight shift and stretch. At the same time, the paper will have a certain deformation after absorbing the fountain solution and the ink. To compensate for this irresistible defect, the print quality belt In order to influence, there are trapping processes in the printing. In traditional printing, trapping settings are generally performed in prepress design and production software. This article takes Heidelberg QM DI46-4 as an example to discuss the trapping control in digital printing.
First, trapping basic theory 1. The concept of trapping In multi-color printing, in order to obtain the best printing effect, it must be ensured that there is a very accurate overlay accuracy throughout the printing process. However, in the actual printing, due to the deformation of the paper, when the four-color overprinting is performed, the printing position of each color image on the paper will have a certain degree of offset, and the substrate color of the printing material will show a small amount. White line. In order to avoid similar displacements, the overprint range of each color patch must be adjusted. The overlap or expansion of this color patch is called trapping. The following discussion mainly discusses two trap types:
(1) Extend the object by expanding or contracting.
(2) Calculate the color value and position of a color band from the edge pixel values ​​where the color patches intersect.
2. Trapping conditions In general, trapping is required when two or more color blocks with large color differences are connected. When the "Easy Trap" threshold (ie, the degree of color difference) is defined for each trapping program, the trapping level is automatically activated. During color separation, QM-DI-RIP calculates and evaluates the entire process during the interpretation of the PS file. If the percentage value of the color difference is greater than or equal to the trap threshold, an extended ribbon will be automatically generated (that is, trapping ). The precondition for this process is that the separation process of the file must be performed in QM-DI-RIP. This kind of trapping method is suitable for almost all objects. The only exceptions are objects that cannot be used for pictures and gradients. For such objects, they can only be processed with trapping techniques that are expanded or shrunk. If there are two adjacent objects, one of which has a color component value that is the same as the color component of the other object (if both contain 100% of cyan color), the other color component values ​​do not vary greatly. There is no need to trap, and the common color components make it very unlikely that there will be blank edges between them.
3. External expansion and internal shrinkage The trapping technology of external expansion and internal shrinkage causes the adjacent color blocks to be overprinted. The size of a certain color block does not change. The size of another color block changes, and the color of the overprinted portion will be automatically formed and depends on the darkness. Hue color blocks. As for what kind of color blocks need to be expanded, what kind of color blocks need to shrink is described as follows:
(1) Expansion. The foreground image is enlarged in size so that it is overprinted on a hollow background, the background patch size remains the same, and the foreground block size expands to a hollow background.
(2) Contraction. If the foreground block size does not change, the hollow part of the background color is reduced. This method is a background object shrinking the foreground object.
4. Trap Color Trapping colors are calculated from the common color components of adjacent colors.
5. Trap color adjustment practice shows that the calculated trapping color has a higher saturation, which appears to be very inappropriate on the printed image, and its effect is far less than an extension of brightness between adjacent objects. In "Easy Trap" mode, each color value of the trapping color will be reduced by a certain percentage. After the trap color value is reduced by 40%, the trapping section is not so obvious.
6. Trapping direction The trapping direction depends on the color brightness of the adjacent objects. The general rule is: extending from light to dark.
7. Centerline Trap In order to obtain high-quality fonts, it is recommended to use centerline trapping. In this way, the font structure can be well preserved without being covered by traps. This trapping occurs evenly at the junction of color patches.
8. The trapping of small fonts due to trapping can cause the edges of small fonts to have a certain degree of blurring, making the recognition rate of the characters lower. In "East Trap" mode, if the size of the text is within the set font size, the trap width will be automatically reduced when trapping.
9. Thin trapping lines will be covered in whole or in part if you use common trapping. In "Easy Trap" mode, the program will calculate the ratio between the trap width and the width of the thin line, and according to this ratio, reduce the trap width.
10. Trap of objects superimposed on images and gradients Objects and text superimposed on images and gradients will change their trapping direction due to the constantly changing brightness of pixel colors. To avoid such situations, objects and texts superimposed on images and gradients will use trapping techniques that expand and shrink in "Easy Trap" mode. For small fonts, it is recommended to use centerline trapping to preserve the font structure.
11. Automatically shrinking black people Ultra-black is often used to obtain maximum saturation in prints. Ultra black contains 100% black and corresponding proportions of blue, yellow, and yellow. The general settings are 50%C, 50%M, 50%Y, 100%B. If overprinting is not accurate, a colored border will appear around the black block. By narrowing the overlapping range of cyan, magenta, and yellow, you can avoid such situations. This shrinking function, that is, the reduction of super black and other color component ranges is provided by the "Autochoke Superblace" attribute.
12. 100% Overprinting If a 100% black foreground is superimposed on a colored background, all backgrounds in black will be hollowed out (ie "knocked out") at RIP. If overprinting is not correct, a white or light-colored border will appear between the colored background and the black foreground. To avoid this, the black setting is "100% Overprint" (Overprint 100%). In RIP, the background is not hollowed out and foreground black is completely overprinted in the background color.
Second, "Auto trap" (Easy trap) mode 1. Using the RIP program, select the Configure RIP... option from the QM-DI-RIP pull-down menu. The Connigig RIP dialog box appears.
2. The Extras->Configure RIP Extras window opens. Select "EasyTrap" and click the "Add" button. The "Enable Feature" dialog appears. Enter the license number in the input box and confirm the exit. The state of the "Enable" column corresponding to "Easy Trap" can be switched between "Yes" and "No".
3. Turn off "Configure RIP Extras" and "Configure RIP" and the "Easy Trap" function will work.
Third, the trapping parameters set trapping parameters can be set in the trapset. Based on different trap widths, three trapsets are set at the factory: a narrow trap width for Light, a moderate trap width for Mid, and a trap width for Heavy. The trapset can be copied, modified or preset (set according to the characteristics of the page setup or calibration)
Activate/preset trapsets: Select "Trapping Manager" from the "OutpUt" drop-down menu. The "Trapping Manager" dialog appears. Select the default trapping settings.
Click "Edit" to reset or edit the trapping parameters, or click "New" to create a new trapping setting name; "Trap Specifications" dialog box opens Name: Enter the name of the trapping settings in this box;
Centerline Iuminance threshold: If this box is activated, traps will be generated between two adjacent colors. Enter the difference in brightness of the adjacent objects in the input box.
Trap widty/stroke width limit: Enter the limit percentage value between the desired trap width and the retract width.
Auto choke superblbCk: If this box is activated, the trap width of the color values ​​of C, M, and Y components will be reduced accordingly. This setting applies only to text and objects using super black;
Normal trap width: Enter the trap width in this box;
Blacsk trap width: Enter the black trap width in this box;
Image/vignette trap width: Enter the trapping value of the object that intersects the picture and the gradient in this box;
Text <... pts trap width: Enter the font size in this box. All fonts with a font size less than this limit will use the trap width set in ?. Units: Select the unit of measure;
Trap threshold: The input value in this box determines the threshold for trap generation. For different component colors, enter the percentage of difference between adjacent colors.
Objects which Intersect images/vignettes (objects that intersect the picture and the gradient): Select the trapping technique based on the objects that intersect the picture and the gradient. Options are expanded, indented, centerline, Automatic mode (Automatically select the outer or inner extent according to the brightness of the color) and no trapping, enter the width value in "Image/vignette trap Width".
Text which Intersects images/vignettes: Select the trapping technique to be used in the drop-down box. The options are External, Indent, Centerline, Auto (Automatically selected based on the height of the color. (Extend or shrink) and trapless, enter the width value in "Image/vignette trap width".
Trap color, select one of the three forms of trapping color in the drop-down box. Trapping is generally generated by performing color calculations according to standard settings based on the color components of adjacent objects. If the printing effect of the trapping color has a higher saturation, each color value becomes a corresponding percentage reduction according to the "Reduce" setting of the box, this appropriate percentage value is controlled in "Option", and the "Highlight" setting It is generally used only for inspection and proofing. With this setting, all traps can be clearly displayed on the print in a single color mode.
Option (more options): When selected, the "Trapping Ontion" dialog box appears. In the "Trap Reduceiltons" field, enter the percentage value to be reduced for each color value.
In the "Image & Vignette Color" area, enter the percentage value of the trapping color reduction for the picture and gradient;
"Do not trap jobs with more than ? items": If this box is activated, trapping values ​​are calculated for each object during the interpretation. If the number of objects exceeds the entered maximum value, the calculation stops. In the "QM-DI-RIP" window, an information message appears that the number of objects for trapping calculation exceeds the set maximum value."
After making various settings in the window, click "OK" to set the save and exit.
4. Trapping the Page Setup Setting the parameters of the trapping settings must point to the page setup so that the information arrives on the printed page and is set via "Page Setup Manager". Turn off "Start Inputs".
When the "Page Setup Manager" sub-item is selected, the "Page setup Manager" window opens and a list of saved page settings can be seen.
The trapping settings can be specified in the following ways. Click Edit to select a page setup item. Click Copy to set this page for backup. The backup file will be listed under this file item. Click New to create a new page setup. (Note: New page setup must also set other QM-DI-RIP parameters.) Select a page setup. After selecting (Edit, Copy, New), the Page Setup window opens. Activate the "Separate color jobs" item so that the separation of files can be performed in QM-DI-RIP. Click the "UCR & TraP..." button. The "UCR & Trap" setting screen appears. All the trapping settings are listed in "Tracing" on this screen. Select the required trap settings and confirm the exit.
For page settings generated with Cooy or New, first click the "Save As ..." button in the page setup window. The "Save Setup" window appears. Enter a name in the "Save As" input field of the window.