Differences

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--- loading_20a_20gif_20or_20jpeg_20image [2018/03/31 13:19] – external edit 127.0.0.1
+++ loading_20a_20gif_20or_20jpeg_20image [2024/01/05 00:22] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
 =====Loading a GIF or JPEG image=====
-//by Richard Russell, September 2008//\\ \\  The main Help documentation describes how to [[http://www.bbcbasic.co.uk/bbcwin/manual/bbcwine.html#gifjpeg|display a GIF or JPEG image]] on the main output window, but you may wish to perform other operations on an image such as accessing its data or displaying it in a static control. In such cases you are likely to need a **handle** to the image.\\ \\  The function below operates in a similar way to **SYS "LoadImage"** except that it works with JPEG, GIF, BMP, ICO, EMF or WMF images. You can alternatively use the function **FNloadimagegdip2** listed at [[/Loading%20a%20PNG%20or%20TIFF%20image|Loading a PNG or TIFF image]] because that will load GIF and JPEG images too, and gives better results when the image is very large or needs to be scaled.\\ \\
+//by Richard Russell, September 2008//\\ \\  The main Help documentation describes how to [[http://www.bbcbasic.co.uk/bbcwin/manual/bbcwine.html#gifjpeg|display a GIF or JPEG image]] on the main output window, but you may wish to perform other operations on an image such as accessing its data or displaying it in a static control. In such cases you are likely to need a **handle** to the image.\\ \\  The function below operates in a similar way to **SYS "LoadImage"** except that it works with JPEG, GIF, BMP, ICO, EMF or WMF images. You can alternatively use the function **FNloadimagegdip2** listed at [[/Loading%20a%20PNG%20or%20TIFF%20image|Loading a PNG or TIFF image]] because that will load GIF and JPEG images too, and gives better results when the image is very large or needs to be scaled.
+<code bb4w>
         DEF FNloadimage(file$, RETURN cx%, RETURN cy%, par%)
         LOCAL iid{}, bmp{}, ix%, iy%, hbm%, hcopy%, pic%, ole%, olpp%, text%
@@ Line 42: / Line 44: @@
         = hcopy%
-The parameters to the function are the filename (or URL) of the image, the required width and height (in pixels) and a flag to indicate whether you want the **aspect ratio** to be preserved or not. Note that a filename must contain the drive name (e.g. **C:**) to distinguish it from an internet URL. The returned value is a **handle** to the image, or zero if the image cannot be found or opened.\\ \\  If the required width and/or height values are supplied as zero then the actual width and/or height of the original image are used. Thus if a non-zero value is supplied for the width and zero is supplied for the height, the image will be scaled horizontally (if required) but not vertically; however if the **preserve aspect ratio** flag is set to TRUE, the then image //will// be scaled vertically to preserve the correct shape.\\ \\  The actual dimensions of the (possibly scaled) image are returned in the second and third parameters, therefore they must be supplied as **variables** rather than as **constants**. Thus if you don't want to scale the image call the function as follows\\ \\
+</code>
+The parameters to the function are the filename (or URL) of the image, the required width and height (in pixels) and a flag to indicate whether you want the **aspect ratio** to be preserved or not. Note that a filename must contain the drive name (e.g. **C:**) to distinguish it from an internet URL. The returned value is a **handle** to the image, or zero if the image cannot be found or opened.\\ \\  If the required width and/or height values are supplied as zero then the actual width and/or height of the original image are used. Thus if a non-zero value is supplied for the width and zero is supplied for the height, the image will be scaled horizontally (if required) but not vertically; however if the **preserve aspect ratio** flag is set to TRUE, the then image //will// be scaled vertically to preserve the correct shape.\\ \\  The actual dimensions of the (possibly scaled) image are returned in the second and third parameters, therefore they must be supplied as **variables** rather than as **constants**. Thus if you don't want to scale the image call the function as follows
+<code bb4w>
         cx% = 0
         cy% = 0
         himage% = FNloadimage(filename$, cx%, cy%, FALSE)
-Alternatively if you are not interested in knowing the actual dimensions you can modify the function definition by removing the **RETURN** qualifiers:\\ \\
+</code>
+Alternatively if you are not interested in knowing the actual dimensions you can modify the function definition by removing the **RETURN** qualifiers:
+<code bb4w>
         DEF FNloadimage(file$, cx%, cy%, par%)
-With this modification you can supply constant values (e.g. 0) as parameters.\\ \\  When you have completely finished with the image you should delete the handle as follows:\\ \\
+</code>
+With this modification you can supply constant values (e.g. 0) as parameters.\\ \\  When you have completely finished with the image you should delete the handle as follows:
+<code bb4w>
         SYS "DeleteObject", himage%
-To use the **FNloadimage** function to display an image in a **static control** see this [[/Displaying%20a%20JPEG%20or%20GIF%20in%20a%20picture%20box|article]].\\ \\  To access the data of the image you can use the **SYS "GetDIBits"** API as follows:\\ \\
+</code>
+To use the **FNloadimage** function to display an image in a **static control** see this [[/Displaying%20a%20JPEG%20or%20GIF%20in%20a%20picture%20box|article]].\\ \\  To access the data of the image you can use the **SYS "GetDIBits"** API as follows:
+<code bb4w>
         cx% = 0
         cy% = 0
@@ Line 73: / Line 91: @@
         SYS "DeleteObject", himage%
         IF num% <> cy% ERROR 100, "GetDIBits failed"
-This provides the image data in 'top-down' format as RGB triplets stored at **imagedata%**; if you require a different data format modify the members of the **bmih** structure accordingly. Note that each line of image data is always padded (if necessary) to a multiple of four bytes.\\ \\  If the image data may be too large to be stored on the heap (possibly with **HIMEM** increased) then you can instead allocate the memory using the Windows API:\\ \\
+</code>
+This provides the image data in 'top-down' format as RGB triplets stored at **imagedata%**; if you require a different data format modify the members of the **bmih** structure accordingly. Note that each line of image data is always padded (if necessary) to a multiple of four bytes.\\ \\  If the image data may be too large to be stored on the heap (possibly with **HIMEM** increased) then you can instead allocate the memory using the Windows API:
+<code bb4w>
         SYS "GlobalAlloc", &40, bmih.biSizeImage% TO imagedata%
         IF imagedata% = 0 ERROR 100, "Insufficient memory"
+</code>
 but in this case don't forget to free the memory later.