The intent of this thread is to explain how color management can be used in VB6. There may be code samples included in some posts and/or links where code samples can be found. This thread will be updated as needed. Per the posting rules of the codebank, 'tutorial' like threads are ok here.
Some definitions/terms used throughout
Color Management: The primary goal is to obtain a good match across color devices; for example, the colors of one frame of a video should appear the same on a computer LCD monitor, on a plasma TV screen, and as a printed poster. Color management helps to achieve the same appearance on all of these devices. For Microsoft's definition, description & justification, see this link. Another reference can be found here that attempts to explain color management in layman terms but also goes indepth
Color transformation: The transformation of the representation of a color from one color space to another.
Color Profile: A file that contains matrices and/or look up tables that are used for color transformations.
Color Gamut: A subset of all possible colors relative to a specific color space. Basically a range of colors supported by a color space
Device-Dependent: Expresses colors relative to some other reference space, a subset of colors which can be displayed using a particular monitor or printer, or can be captured using a particular digital camera or scanner.
Device-Independent: Expresses colors in absolute terms. sRGB (standard RGB) is such a color space.
Why do I want to support color management and how much effort is needed? "Why" is simple enough. If you are displaying graphics that should always be seen by the user/customer as perfect as possible, then you should support color management. How much of a headache is this? Can be a lot initially. At a minimum, these issues need to be resolved:
- Whatever monitor your application runs on should be calibrated. For the average user, this is not trivial.
- Whatever monitor your application runs on should also have installed device-specific profiles to ensure best color matching
- You need to be able to extract/apply embedded color profiles/data from any image you display, if those profiles exist
- In VB, you need to activate color management for your applications.This is NOT done by default
Even if calibration is not performed nor a manufacturer-supplied color profile is being used, supporting color management for images can produce more accurate colors relative to the source image than would otherwise be displayed on the screen without it. Extraction of color profiles is made easier with the use of GDI+. But some versions have bugs that can prevent some data extraction and GDI+ does not support extraction on all image formats that support color profile embedding.
Activating color management within VB is the easiest thing you can do, but does very little without the ability of applying embedded image color profiles. Generally speaking, if no profile has been assigned to the monitor, then Windows assumes sRGB color space is in use. And if color profiles are not applied to images, then rendering done by Windows assumes it is between sRGB source and sRGB destination. Bottom line is that color management is prevented. If there is a color profile assigned to the monitor, then activating color management in VB for your display contexts (DCs, hDC properties) may improve color display a bit. Most monitor color profiles are not equivalent to sRGB, so color transformations are likely to occur.
In the next sections, I'll discuss how you can extract color profiles from images and various ways to apply those profiles to the images for a more accurate display. Also, VB6 users may or may not use GDI+ for the lion's share of rendering images, so I'll also try to show how these profiles can be used with both GDI and GDI+. But for simplicity sake, let's just say that enabling color management for embedded profiles will require the use of both GDI and GDI+
Some examples on this site:
Color Management with GDI+
Color Management - Different Approach
Color Management (ICC Profile) support in VB6: guide and sample project
Some definitions/terms used throughout
Color Management: The primary goal is to obtain a good match across color devices; for example, the colors of one frame of a video should appear the same on a computer LCD monitor, on a plasma TV screen, and as a printed poster. Color management helps to achieve the same appearance on all of these devices. For Microsoft's definition, description & justification, see this link. Another reference can be found here that attempts to explain color management in layman terms but also goes indepth
Color transformation: The transformation of the representation of a color from one color space to another.
Color Profile: A file that contains matrices and/or look up tables that are used for color transformations.
Color Gamut: A subset of all possible colors relative to a specific color space. Basically a range of colors supported by a color space
Device-Dependent: Expresses colors relative to some other reference space, a subset of colors which can be displayed using a particular monitor or printer, or can be captured using a particular digital camera or scanner.
Device-Independent: Expresses colors in absolute terms. sRGB (standard RGB) is such a color space.
Why do I want to support color management and how much effort is needed? "Why" is simple enough. If you are displaying graphics that should always be seen by the user/customer as perfect as possible, then you should support color management. How much of a headache is this? Can be a lot initially. At a minimum, these issues need to be resolved:
- Whatever monitor your application runs on should be calibrated. For the average user, this is not trivial.
- Whatever monitor your application runs on should also have installed device-specific profiles to ensure best color matching
- You need to be able to extract/apply embedded color profiles/data from any image you display, if those profiles exist
- In VB, you need to activate color management for your applications.This is NOT done by default
Even if calibration is not performed nor a manufacturer-supplied color profile is being used, supporting color management for images can produce more accurate colors relative to the source image than would otherwise be displayed on the screen without it. Extraction of color profiles is made easier with the use of GDI+. But some versions have bugs that can prevent some data extraction and GDI+ does not support extraction on all image formats that support color profile embedding.
Activating color management within VB is the easiest thing you can do, but does very little without the ability of applying embedded image color profiles. Generally speaking, if no profile has been assigned to the monitor, then Windows assumes sRGB color space is in use. And if color profiles are not applied to images, then rendering done by Windows assumes it is between sRGB source and sRGB destination. Bottom line is that color management is prevented. If there is a color profile assigned to the monitor, then activating color management in VB for your display contexts (DCs, hDC properties) may improve color display a bit. Most monitor color profiles are not equivalent to sRGB, so color transformations are likely to occur.
In the next sections, I'll discuss how you can extract color profiles from images and various ways to apply those profiles to the images for a more accurate display. Also, VB6 users may or may not use GDI+ for the lion's share of rendering images, so I'll also try to show how these profiles can be used with both GDI and GDI+. But for simplicity sake, let's just say that enabling color management for embedded profiles will require the use of both GDI and GDI+
Some examples on this site:
Color Management with GDI+
Color Management - Different Approach
Color Management (ICC Profile) support in VB6: guide and sample project