[VB6] GDI+ Usage & Samples

[LaVolpe]

This project is a teaser to get one's feet wet. For a fully functional usercontrol that is based almost entirely on GDI+, see my alpha image control project.

If you have questions on how to do something with GDI+ that the attached project does not do, please post your question in the Graphics portion of the forum. I do not want, nor intend that this posting become a proxy "GDI+ Forum"

If you have questions about this project then by all means ask away. There may be a few logic errors in the project; as we find those I'll continue to update. Jump to bottom to determine when last updated.

GDI+ is a very handy tool and many coders stay away from it because it appears difficult, at first. So, the classes in this project are aimed at easing you along a bit. GDI+ has 100's of functions and the project herein only touches a small percentage of them. But should be enough for you to get your feet wet without being overwhelmed.

A great site for descriptions of the GDI+ API functions.

I do plan on updating this project from time to time. Things I have knowledge on and have not yet added to the project include GDI+ paths, strings, and regions. The project does include a very complete image processing class, a rendering class, and a pens/brushes class to get you started.

If you want the absolute minimal code to read and display an image at actual size, see post #8 below



Some advantages of using GDI+
:: Load/Save PNGs and TIFFs, even multi-page TIFFs
:: Load and display animated GIFs
:: Alphablending - images, lines, shapes, everything. GDI+ does not use standard RGB colors. All colors are ARGB which includes level of alphablending.
:: Built-in niffty options like rotation, mirroring, on-the-fly pixel transformations and more
:: No manual premultiplication of alpha values
Some disadvantages of GDI+
:: Crashes easy if not used properly. Objects created around other objects (i.e., images) are not actually stand-alone. GDI+ requires the source data to remain present until the GDI+ object is destroyed.
-- Here is the MS KB Article link: http://support.microsoft.com/kb/814675
-- The workaround is to create a DIBSection, then create a GDI+ bitmap from it and destroy the DIBSection
-- But that workaround won't allow access to other images in a multi-image formats (GIFs, TIFFs) and 32bpp become pARGB.
:: In IDE, can crash easily too -- like subclassing, you cannot just hit End or terminate your app from the debug window while GDI+ is running.
:: As mentioned above, a little complicated for new users
:: Does not support all older GDI functions. For example, you can't create an XOR pen with GDI+
:: Requires extra steps to setup for drawing; but like anything new to you, just takes a little getting used to

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Last Edited: Jan 21, 2010 8:50 PM GMT/Zulu
:: Modified primarily for TIFF saving
-- Can now save multiple images with/without attributes applied
-- TIFF images can be saved in 1,4,8,24,32 bit depths - dependent upon source image depth
:: Added another optional rendering quality setting when drawing: PixelOffsetMode
:: Removed requirement of cGDIpRenderer to be passed token class during its function calls.
-- Now entire class can be passed it one time via its AttachTokenClass method
:: Single page TIFFs no longer cache their original source data; more memory savings
Jan 19, 2010 2:20 AM GMT/Zulu
:: Revamped quite a bit
-- To reduce memory usage, PNG, BMP, & JPG no longer cache original data
-- CloneImage routine still had some shortcomings when trying to clone without applying image attributes; fixed
-- Fixed logic error reported by Jonney when cloning rotated images
:: Added additional image types: imageIconPNG & imageCursorPNG to distinguish between PNGs loaded from ico/cur resources
Jan 14, 2010 19:10 PM GMT/Zulu
:: Found 2 memory leaks, one each in 2 different functions; fixed
:: Changed logic when loading new images
-- If new image then all attributes are reset automatically (were not before). Optional load flag prevents this.
-- If multi-image format displays another image within same source; attributes remain (no change from previous logic)
:: CreateCloneWithAttributes renamed to CreateClone. WithAttributes now an optional parameter
:: ImageType property distinguishes between icons and cursors now
:: Reorganized and cleaned up some routines
:: Demo reworked a tad
-- You can now apply multiple attributes to the same image and see results
-- Included sample of saving a multi-page TIFF
Jan 12, 2010 01:10 AM GMT/Zulu
:: Added a little more functionality to the cGDIpImage class
-- GetPixel, SetPixel, ExtraTransparentColor (similar functionality of TransparentBLT)
:: Mirroring was off, had my constants swapped around, fixed
:: When SaveAsOriginalFormat was applied for 32bpp alphablended bitmaps, was saved as 24bpp vs 32pp, fixed
:: Updated demo a bit
-- included SaveAsOriginalFormat, TransparentBLT examples
-- included option to view any image in a multiple image format
-- included option to view image info: size, depth, type
Jan 11, 2010 01:30 AM GMT/Zulu
:: Jonney helped identify a logic error when deciding whether 32bpp images use the Alpha channel and how it is used. Thanx Jonney
...