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@ -28,55 +28,28 @@ |
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* croppdf.c |
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* |
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* This program concatenates all pdfs in a directory by rendering them |
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* as images, optionally scaling the images, and generating an output pdf. |
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* The pdfs are taken in lexical order. Pages are encoded with either |
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* tiffg4 or jpeg (DCT), or a mixture of them depending on input parameters |
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* and page color content. For DCT encoding, the jpeg quality factor |
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* can be used to trade off the size of the resulting pdf against |
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* the image quality. |
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* as images, cropping each image to the foreground region with |
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* options for noise removal and margins, slightly thickens long |
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* horizontal lines (e.g., of a music staff), and to some extent |
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* scales the width to fill a printed page. See documentation for |
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* pixCropImage() for the parameters. |
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* |
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* If the pages are monochrome (black and white), use of the %onebit |
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* flag will achieve better compression with less distortion. |
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* If most of the pages are black and white, but some have color that |
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* needs to be saved, input parameters %onebit and %savecolor should |
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* be both set to 1. Then the pages with color are compressed with DCT |
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* and the monochrome pages are compressed with tiffg4. |
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* The pdfs are concatenated in lexical order, and each image |
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* is encoded with tiffg4. |
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* |
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* The first step is to render the images as RGB, using Poppler's pdftoppm. |
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* Compare compresspdf with cleanpdf, which carries out several cleanup |
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* operations, such as deskewing and adaptive thresholding to clean |
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* noisy or dark backgrounds in grayscale or color images, resulting |
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* in high resolution, 1 bpp tiffg4 encoded images in the pdf. |
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* |
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* Syntax: |
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* compresspdf basedir scalefactor onebit savecolor quality title fileout |
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* Syntax: |
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* croppdf basedir threshold lrclear tbclear edgeclean |
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* lradd tbadd title fileout |
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* |
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* The %basedir is a directory where the input pdf files are located. |
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* The program will operate on every file in this directory with |
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* the ".pdf" extension. |
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* |
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* The %scalefactor is typically used to downscale the image to |
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* reduce the size of the generated pdf. It should not affect the |
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* pdf display otherwise. For normal text on images scanned at 300 ppi, |
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* a 2x reduction (%scalefactor = 0.5) may be satisfactory. |
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* We compute an output resolution for that pdf that will cause it |
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* to print 11 inches high, based on the height in pixels of the |
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* first image in the set. |
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* |
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* Images are saved in the ./image directory as RGB in ppm format. |
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* If the %onebit flag is 0, these will be encoded in the output pdf |
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* using DCT. To force the images to be 1 bpp, with tiffg4 encoding, set |
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* the $onebit flag to 1. |
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* |
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* The %savecolor flag is ignored unless %onebit is 1. In that case, |
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* if %savecolor is 1, the image is tested for color content, and if |
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* even a relatively small amount is found, the image will be encoded |
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* with DCT instead of tiffg4. |
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* The %lrclear and %tbclear parameters give the number of background |
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* pixels to be added to the foreground region. |
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* |
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* The %quality is the jpeg output quality factor for images stored |
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* in the pdf. Use 0 for the default value (50), which is satisfactory |
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* for many purposes. Use 75 for standard jpeq quality; 85-95 are very |
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* high quality. Allowed values are between 25 and 95. |
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* The %edgeclean parameter is used to remove edge noise, going from |
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* 0 (default, no removal) to 15 (maximally aggressive removal). |
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* |
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* The %title is the title given to the pdf. Use %title == "none" |
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* to omit the title. |
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@ -84,14 +57,9 @@ |
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* The pdf output is written to %fileout. It is advisable (but not |
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* required) to have a '.pdf' extension. |
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* |
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* The intent is to use pdftoppm to render the images at 150 pixels/inch |
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* for a full page, when scalefactor = 1.0. The renderer uses the |
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* mediaboxes to decide how big to make the images. If those boxes |
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* have values that are too large, the intermediate ppm images can |
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* be very large. To prevent that, we compute the resolution to input |
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* to pdftoppm that results in RGB ppm images representing page images |
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* at about 150 ppi (when scalefactor = 1.0). These images are about |
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* 6MB, but are written quickly because there is no compression. |
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* As the first step in processing, images are saved in the ./image |
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* directory as RGB at 300 ppi in ppm format. Each image is about 26MB. |
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* Delete those images after use. |
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* |
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* N.B. This requires the Poppler package of pdf utilities, such as |
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* pdfimages and pdftoppm. For non-unix systems, this requires |
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@ -123,21 +91,20 @@ l_int32 main(int argc, |
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char buf[256]; |
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char *basedir, *fname, *tail, *basename, *imagedir, *title, *fileout; |
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l_int32 threshold, lrclear, tbclear, edgeclean, lradd, tbadd; |
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l_int32 render_res, onebit, savecolor, i, n, ret; |
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l_float32 scalefactor; |
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l_int32 render_res, i, n, ret; |
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SARRAY *sa; |
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if (argc != 10) |
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return ERROR_INT( |
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"Syntax: croppdf basedir threshold lrclean tbclear edgeclean " |
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"Syntax: croppdf basedir threshold lrclear tbclear edgeclean " |
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"lradd tbadd title fileout", __func__, 1); |
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basedir = argv[1]; |
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threshold = atoi(argv[2]); |
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lrclear = atoi(argv[3]); /* set to 1 to enforce 1 bpp tiffg4 encoding */ |
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tbclear = atoi(argv[4]); /* set to 1 to enforce 1 bpp tiffg4 encoding */ |
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edgeclean = atoi(argv[5]); /* jpeg quality */ |
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lradd = atoi(argv[6]); /* set to 1 to enforce 1 bpp tiffg4 encoding */ |
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tbadd = atoi(argv[7]); /* set to 1 to enforce 1 bpp tiffg4 encoding */ |
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lrclear = atoi(argv[3]); |
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tbclear = atoi(argv[4]); |
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edgeclean = atoi(argv[5]); |
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lradd = atoi(argv[6]); |
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tbadd = atoi(argv[7]); |
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title = argv[8]; |
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fileout = argv[9]; |
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setLeptDebugOK(1); |
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@ -184,17 +151,13 @@ SARRAY *sa; |
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} |
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sarrayDestroy(&sa); |
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/* Optionally binarize, then scale and collect all images in memory. |
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* If n > 100, use pixacomp instead of pixa to store everything |
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* before generating the pdf. |
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* When using the onebit option, It is important to binarize |
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* the images in leptonica. Do not let 'pdftoppm -mono' do |
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* the binarization, because it will apply error-diffusion |
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* dithering to gray and color images. */ |
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/* Process each image and collect all resulting 1 bpp images |
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* in memory. If n > 200, use pixacomp instead of pixa to |
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* store the images before generating the pdf. */ |
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sa = getSortedPathnamesInDirectory(imagedir, NULL, 0, 0); |
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lept_free(imagedir); |
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sarrayWriteStderr(sa); |
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lept_stderr("compressing ...\n"); |
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lept_stderr("croping ...\n"); |
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cropFilesToPdf(sa, threshold, lrclear, tbclear, edgeclean, |
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lradd, tbadd, title, fileout); |
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danblooomberg
2 years ago