Hi Everybody,
I am just a newbie here who is trying to use the iText for some PDF related functions in my development job. Here I got some questions about how the iText handle about the image storage inside the PDF file:
From the iText tutorial, it mentioned: "Remark that the resolution of an image that is added without scaling will be 72dpi by default. If an image is placed with a scaling of 50% the the resolution will be 144. With lower scalings the resolution will increase because the pixels are the same but the size will be smaller. To put a picture with 300dpi use a scaling of 72/300=24%. For instance: if you have a 5X5 inch image that you scan at 300 dpi, the resultant image is 1500X1500 pixels (5X300 = 1500). When you place this image in the pdf with a scaling of 24% (72/300 = 0.24), the image in the pdf will be 5X5 inch with 1500X1500 pixel at 300 dpi. The image will always be 1500X1500 pixel whatever the size. "
As my understanding, which means the resolution dpi of the image will only be decided by the original image source data as well as the size scaling of the display area of that image in the generated PDF file.
But I am also wondering how can I adjust the resolution if needed.
Seems the com.lowagie.text.Image class has the Method of "setDpi()" and also methods for retrieving the dpi info, which are "getDpiX()" and "getDpiY()";
I've write some codes to see how those methods work, which as following:
Image jpg = Image.getInstance("test.jpg");
System.out.println("Original Dpi: x="+jpg.getDpiX()+" y="+jpg.getDpiY());
jpg.setDpi(500,500);
System.out.println("After Setting Dpi: x="+jpg.getDpiX()+" y="+jpg.getDpiY());
jpg.scalePercent(50f);
System.out.println("After Scaling Dpi: x="+jpg.getDpiX()+" y="+jpg.getDpiY());
document.open();
document.add(jpg);
However, the output result kind of confused me about the idea. Because it seemed that the "setDpi()" Method will change the values of "getDpiX()" and "getDpiY()", and the "scalePercent()" method has nothing to do with the results of those two methods, besides, no matter what dpi value I set with the "setDpi()" Method, the generated PDF file size will be just the same.
If anybody can give a clear explanation on this issue, that will be really appreciated!
Thank you very much!
Best,
Han
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No. 86-756-3398808
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