file functions

HCR-Edit can read and write a variety of different image file formats.

• reading:
  

  opens an image file via standard dialog.

  the file formats currently supported are:
  
  • Portable Network Graphic (PNG)
    HCR-Edit can read 24 and 48 bit rgb as well as 8 and 16 bit grayscale files.
  • TGA
    only uncompressed files with 24 bit rgb, 8 bit files with palette are read as grayscale.
  • Portable Pixmap (PPM)/Portable Graymap (PGM)
    HCR-Edit can read PPM/PGM files in both ASCII and binary form with 8 or 16 bit values. With ASCII files this function is also capable of reading float values.
  • High Dynamic Range Image (HDR)
    Radiance RGBE high dynamic range image files can be read with HCR-Edit.
  • Raw binary data
    Raw binary data data of various forms can be read, the format is specified in a separate dialog box.


• writing:
  

  saves the current image using the adjustments. Usually color values are clipped to a finite range defined by the file format. For High dynamic range and floating point formats the values are not clipped and only brightness, contrast and gamma correction are applied.

  the file formats currently supported are:
  
  • Portable Network Graphic (PNG)
    like for reading 24/48 bit rgb and 8/16 bit grayscale format are supported.
  • TGA
    HCR-Edit writes uncompressed 24 bit rgb and 8 bit grayscale TGA files.
  • portable pixmap (PPM)
    binary PPM files can be written with both 8 and 16 bit accuracy. Grayscale (PGM) files are supported too.
  • High Dynamic Range Image (HDR)
    Radiance RGBE high dynamic range image files
  • RAW 32 bit float data


• merging:
  

  opens the merging dialog.

  with this function you can add a horizontal stripe from a second image file and thereby combine an image from partial renders for example.
  
  Currently only PNG files are supported here.
  

general editing functions

New_Color = ((Old_Color-0.5)*Contrast+0.5+Brightness)Gamma

The main menu

• file:
  • open: opens an image file.
  • merge: merges a second image into the current one.
  • save: saves current image to a file.
  • save as: saves current image to a file using a new filename.
  • close: closes current image file.
  • history: accesses recently opened images.
  • exit: closes the program.


• edit:
  • undo: undoes the last modifiaction.
  • copy: copies current image to clipboard.
  • paste: pastes image data from clipboard.


• view:
  • color curves: displays the color curves adjustment window.
  • focal blur: displays the focal blur window.
  • levels: displays the levels adjustment window.
  • exposure: displays the exposure adjustment window.


• options:
  • Undo enabled: toggles the undo function.


• help:
  • documentation: loads the program documentation.
  • about: shows the program info box.

The toolbar

Supplies shortcuts to:

• file->open
• file->save
• file->merge
• edit->copy
• edit->paste
• edit->undo
• view->color curves
• view->color levels
• view->exposure
• view->focal blur
• help->documentation
• file->exit

The statusbar

Shows some status information:

• On the left the position and color value (in POV-Ray notation) are shown when the mouse pointer is inside the image display. Furthermore general status informations are shown here.
• In the middle field you can see a progress indicator when a file or modification function is in progress.
• The right field shows information about the file type of the current file being handled.

The raw import window

HCR-Edit allows detailed control over the the file format specifications when importing raw data. This way a large variety of file formats can be read. The adjustments are made in this dialog.

First the width and height of the image have to be specified (in pixel) the height can be concluded automatically from the file size if the 'auto' checkbox is activated.

Then the number of header bytes to be skipped can be specified.

Finally you have to adjust the format of the actual data in the file. There are 4 prepared settings for 8 and 16 bit single channel integer data as well as 3 channel data in order RGB. Furthermore 32 bit (single) and 64 bit (double) float data can be loaded as both single channel (grayscale) and rgb.

Other custom integer formats have to be defined using the custom settings.

These settings consist of the number of bytes per pixel and per data value and the starting byte for each value. This way you can also extract three color channels from file formats containing more than three data channels.

The color curves window

The color curves are transmission curves for the color values of the image. a color value x is translated into a value y according to a spline function.

If same for all channels is checked there is only one curve for all color channels no matter if the image is grayscale or rgb.

• Clears the spline knots and creates a linear transmission curve.
• Opens a standard file dialog for loading a curve from a file.
• Opens a standard file dialog for saving the current curve from a file.

Depending on whether or is pressed there is a new knot added to the active spline or the active knot is deleted when the right mouse button is pressed.

The remaining buttons can be used for activating the different channels and editing the curves individually.

The exposure window

The exposure settings are applying a exponential film exposure simulation to the image. The color values are trated with the formula:

The values for Gain and Exposure can be adjusted in the window.

The focal blur window

This function is intended for applying focal blur to an image. For this purpose it uses depth data in form of a second grayscale image that has to fit to the image the function is applied to.

A lot of 3D programs have functions to generate a depth image from a scene (also known as z-buffer). With POV-Ray you can texture the whole scene in ambient white and add an ambient black fog or apply a spherical pattern texture ranging from black to white to get the depth output. Don't forget to add hf_gray_16 on to global_settings to get 16 bit accuracy output.

In addition to the data file there are 3 values to control the blur:

• The amount is the maximum intensity of the blur. Any positive values are allowed.
• The bleed reduction should reduce bleeding at borders between strongly blurred and less blurred regions. This function is very experimental. A value of 0 turns it off.
• The radius specifies the size of the blur matrix. This strongly influences the intensity of the blur. Higher values make the calculation very slow.

Finally you can control which distances to blur and which to maintain untouched with a transmission curve for the depth data. The curve editor works like in the color curve window.

The merging dialog

This window allows to merge the content of a second image file (or parts of it) into the currently loaded image. This function is mainly intended for merging partial renders into one image. Right now you can only specify the vertical position, therefore the function is only suited for merging horizontal stripes, for example renderd with POV-Ray using the +sr / +er options. HCR-Edit is also capable to read PNG files from interrupted POV-Ray renders.

The image file to be merge is opened using the Add button at the upper right of the window. Only PNG files are possible here right now.

The vertival starting position for the merged stripe is either given in the Position box or interactively using the mouse in the preview window. You can either merge the whole image or only a specified number of lines. For precise positioning of the image you can magnify the preview window with the Zoom function.

Pressing the Merge button finally merges the image into the into the main image data.

The levels window

The levels tool adjusts color range and balance of the loaded image. The image histogram is displayed for helping to find the correct values.

The Input levels specify what cange of color values from the unmodified data is supposed to be used for the resulting image. Values above or below this range are clipped. For the transit between those values you can choose a gamma exponent. This transformation applied to a black-white gradient is displayed below the histogram.

The Output levels specify what range of the possible output values is supposed to be used in the resulting image.

When editing color images each of these adjustments is available for each color channel separately and for all channels combined. For editing the different channels use the button set on the upper left.

There is an additional automatic selection of values available through the Auto button. This function is based on an analysis of the histogram.

The small button next to the channels selector expands controls for specifying the histogram resolution and a parameter for the auto adjustment.