fortran-gdlib

Fortran binding for the GD graphics library https://libgd.github.io/.

Table of Contents

• Requirements
• Compiling
• Running the Tests
• Using the Library
• Current status and Aims
• Image Gallery
  • Primitive Drawing Operations
  • Font Handling
  • Image Processing
  • Animation
• Video Manipulation

Requirements

• Fortran-2008 compatible Fortran compiler (tested with gfortran 11)
• libGD and its dependencies

Compiling

Edit the Makefile such that ist fits both your Fortran environment and your installation of the GD Library. The library is then created (along with an example applications) by invoking the make command.

Running the tests

Change to the tests subdirectory and run the run_tests.sh script using the system shell (For Windows there is also a unn_tests.bat script). The output files can then be found in the outpics subdirectory of tests.

Using the Library

The library is a thiny wrapper around the GD C library, so that the documentation of the C library can actually be used for the wrapper, too. A compilation of rescources concerning interfacing between C and Fortran can be found in the documentation of GTK Fortran by Vincent Magnin and others: https://github.com/vmagnin/gtk-fortran/wiki/Fortran-interoperability-with-C.

I think the most important points one has to get used to are:

• Use the iso_c_binding intrinsic module and the data typed defined there for C compatibility.

• Add the c_null_char at the end every string.

• Use a C type file handling using the wrapper functions gd_fopen for the fopen function of the C library and gd_fclose for the fclose function of the C standard library. So unfortunately the binding does not integrate well in the Fortran way of handling files (and there is no easy way to implement this in a portable way).

To use the library for own projects, you have to copy the library files (In the case of Unix-like systems fortran_libgd.a ist the static and fortran_libgd.so the dynamically library binary) and the module file (fortran_libgd.mod in the case of gfortran, the name may vary among different compilers) to locations in the file system where they are found by the compiler. In the case of the shared library, its position has to be included in the corresponding search path.

Note: The library files are not necessarily compatible among diffent compilers or even different versions of the same compilers.

Current status and aims

Currently it is in an early state and supports only a subset of the functions provides by the GD library. Still, I think that the most relevant functionality is already there. My plan is to gradually add more functions, but it is unlikely that the wrapper will ever cover the complete functionality of the GD librrary.

If you miss sopme functionality just drop me a message or -- even better -- add that functionality and and fill a pull request.

The current implementation status is (✅: implemented und tested, ❓: implemented, but not tested, ✘: not implemented; if a function is not mentioned here, it is likely not supported)

• gdAlphaBlend (❓)
• gd_fclose (✅)
• gdClearErrorMethod (✘)
• gdFontCacheShutdown (❓)
• gdFontGetGiant (✅)
• gdFontGetLarge (✅)
• gdFontGetMediumBold (✅)
• gdFontGetSmall (✅)
• gdFontGetTiny (✅)
• gd_fopen (✅)
• gdImageAAblend (✘)
• gdImageAlphaBlending (❓)
• gdImageArc (✅)
• gdImageAlpha (❓)
• gdImageBlue (✅)
• gdImageBoundsSave (✘)
• gdImageBrightness (❓)
• gdImageClone (❓)
• gdImageChar (❓)
• gdImageCharUp (❓)
• gdImageColor (❓)
• gdImageColorClosest (✘)
• gdImageColorClosestAlpha (✘)
• gdImageColorClosetExact (✘)
• gdImageColorClosetExactAlpha (✘)
• gdImageColorAllocate (✅)
• gdImageColorAllocateAlpha (❓)
• gdImageColorDeallocate (✘)
• gdImageColorPaletteCopy (✘)
• gdImageColorReplace (❓)
• gdImageColorReplaceArray (✘)
• gdImageColorReplaceCallback (✘)
• gdImageColorReplaceThreshold (✘)
• gdImageColorResolve (✘)
• gdImageColorResolveAlpha (✘)
• gdImageColorsTotal (❓)
• gdImageColorTransparent (✘)
• gdImageConvolution (✘)
• gdImageCompare (❓)
• gdImageContrast (❓)
• gdImageCopy (❓)
• gdImageCopyGaussianBlurred (❓)
• gdImageCopyMerge (❓)
• gdImageCopyMergeGrey (❓)
• gdImageCopyResampled (❓)
• gdImageCopyResized (❓)
• gdImageCopyRotated (✅)
• gdImageCreate (✅)
• gdImageCreateFromGif (❓)
• gdImageCreateFromFile (✅)
• gdImageCreateFromPng (✅)
• gdImageCreatePaletteFromTrueColor (✅)
• gdImageCreateTrueColor (✅)
• gdImageCrop (✅)
• gdImageCropAuto (✅)
• gdImageCropThreshold (✅)
• gdImageDashedLine (✅)
• gdImageDestroy (✅)
• gdImageEdgeDetectQuick (✅)
• gdImageEllipse (✅)
• gdImageEmboss (❓)
• gdImageFile (❓)
• gdImageFill (✅)
• gdImageFilledArc (✅)
• gdImageFilledEllipse (✅)
• gdImageFilledPolygon (❓)
• gdImageFilledRectangle (✅)
• gdImageFillToBorder (✘)
• gdImageFlipBoth (❓)
• gdImageFlipHorizontal (❓)
• gdImageFlipVertical (❓)
• gdFontCacheShutdown (❓)
• gdImageGaussianBlur (❓)
• gdImageGetClip (❓)
• gdImageGetInterlaced (❓)
• gsImageGetInterpolationMethod (✘)
• gdImageGetPixel (❓)
• gdImageGetTrueColorPixel (✅)
• gdImageGif (✅)
• gdImageGifAnimAdd (✅)
• gdImageGifAnimAddCtx (✘)
• gdImageGifAnimAddPtr (✅)
• gdImageGifAnimBegin (✅)
• gdImageGifAnimBeginCtx (✘)
• gdImageGifAnimBeginPtr (✅)
• gdImageGifAnimCtx (✘)
• gdImageGifAnimEnd (✅)
• gdImageGifCtx (✘)
• gdImageGifPtr (✅)
• gdImageGrayScale (❓)
• gdImageGreen (✅)
• gdImageInterlace (❓)
• gdImageJpeg (✅)
• gdImageLine (✅)
• gdImageMeanRemoval (❓)
• gdImageNegate (❓)
• gdImageNeuQuant (❓)
• gdImageOpenPolygont (❓)
• gdImagePalettePixel (❓)
• gdImagePaletteToTrueColorp (✘)
• gdImagePixelate (❓)
• gdImagePng (✅)
• gdImagePolygon (❓)
• gdImageRectangle (✅)
• gdImageRed (✅)
• gdImageResolutionX (✅)
• gdImageResolutionY (✅)
• gdImageRotateInterpolated (✅)
• gdImageScatter (❓)
• gdImageScatterColor (❓)
• gdImageSelectiveBlur (❓)
• gdImageSetAntiAliased (❓)
• gdImageSetAntiAliasedDontBlend (❓)
• gdImageSetBrush (❓)
• gdImageSetClip (✘)
• gdImageSetInterpolationMethod (❓)
• gdImageSetResolution (✘)
• gdImageSetStyle (❓)
• gdImageSetThickness (❓)
• gdImageSetTile (❓)
• gdImageSmooth (❓)
• gdImageString (✅)
• gdImageStringUp (✘)
• gdImageString16 (✘)
• gdImageStringUp16 (✘)
• gdImageStringFT (✅)
• gdImageSX (✅)
• gdImageSY (✅)
• gdImageTrueColor (❓)
• gdImageTrueColorPixel (❓)
• gdImageTrueColorToPalette (❓)
• gdImageTrueColorToPaletteSetMethod (❓)
• gdImageTrueColorToPaletteSetQuality (❓)
• gdLayerMultiply (❓)
• gdLayerOverlay (❓)
• gdMinorVersion (✅)
• gdMajorVersion (✅)
• getPixelRgbInterpolated (✘)
• gdReleaseVersion (✅)
• gdSetErrorMethod (✘)
• gdSupportsFileType (❓)
• gdTransformAffineBoundingBox (✘)
• gdTransformAffineCopy (✘)
• gdTransformAffineGetImage (✘)
• gdTrueColorGetAlpha (❓)
• gdTrueColorGetBlue (❓)
• gdTrueColorGetGreen (❓)
• gdTrueColorGetRed (❓)

Image Gallery

Primitive Drawing Operations

Demonstration of primitive Drawing operations (line arcs, filling areas ect..)

Regular polygon wirth 30 corners and diagonals.

Font Handling

Demonstration of the True-Type Font handling capabilities of the Library (the rectangles with quotation marks are indicators that a character is not provided by the current font and not a bug of the library..

Image Processing

Sequence of images of a flower where the first is the unedited one, the next ones arfe the red, green and blue color channels of that image and the last one uses an edge-detection function built-in in GD lib

Animation

Animation of an image that is rotated

Video Manipulation

Using FFMPG it is also possible to use GDlib - and consequently fortran-gdlib - to manipulate videos .

To do so a pipe from (for input) and another pipe to ffmpeg are created. The advantage of this approach is that the internals of the codecs do not have to be known to the program acting as "filter", if the ffmpeg takes care of the the conversion of the input data into raw data that can be handled by the 'filter'. After the manipulation is done, ffmpe3g re-encode the raw output.

Of course, it is also possible to use ffmpeg only for the input of data.

An detailed explanation on the basis of a test program is given in in a .

The method described there is based on a excellent blog entry by Ted Burke which in turn was inspired by a Python solution by Zulko.

While Ted Burke was so kind to give me permission to use his Code as a template for my Fortran example, all bugs are purely my own...