diff --git a/Makefile b/Makefile
index 9ce485e..ed76943 100644
--- a/Makefile
+++ b/Makefile
@@ -59,11 +59,8 @@ base_image/okmpaint.fxf: applications/okmpaint/OkmPaint.okm $(wildcard applicati
 base_image/bg.fxf: applications/bg/main.asm
 	$(FOX32ASM) $< $@
 
-base_image/bg.raw: applications/bg/bg.inc
-	$(FOX32ASM) $< $@
-
-applications/bg/bg.inc: applications/bg/bg.png
-	$(GFX2INC) 640 480 $< $@
+base_image/bg.bmp: applications/bg/bg.bmp
+	cp $< $@
 
 base_image/launcher.fxf: applications/launcher/main.asm $(wildcard applications/launcher/*.asm) applications/launcher/icons.inc
 	$(FOX32ASM) $< $@
@@ -105,7 +102,7 @@ FILES = \
 	base_image/foxpaint.fxf \
 	base_image/okmpaint.fxf \
 	base_image/bg.fxf \
-	base_image/bg.raw \
+	base_image/bg.bmp \
 	base_image/launcher.fxf \
 	base_image/ted.fxf
 
diff --git a/applications/bg/bg.bmp b/applications/bg/bg.bmp
new file mode 100644
index 0000000..c5f7bf2
Binary files /dev/null and b/applications/bg/bg.bmp differ
diff --git a/applications/bg/bg.png b/applications/bg/bg.png
deleted file mode 100644
index 5e668f0..0000000
Binary files a/applications/bg/bg.png and /dev/null differ
diff --git a/applications/bg/main.asm b/applications/bg/main.asm
index fb2b90a..03b4353 100644
--- a/applications/bg/main.asm
+++ b/applications/bg/main.asm
@@ -1,27 +1,229 @@
 ; background image utility
 
+; global registers
+; r30: pointer into `buffer`
+; r29: file offset of topmost bitmap line
+; r27, r28: width, height of image
+; r26: line stride of file (width * bytes_per_pixel rounded up to align to 4 bytes)
+; r25: pointer into background framebuffer
+; r24: bytes per pixel
+; r23: min(width, 640)
+; r20: stream pointer (for terminal io)
+
+; BMP features not yet supported
+; - Negative height (implies image data is flipped vertically)
+; - Bits per pixel besides 24
+; - Compression
+; - Any sort of YUV?
+
+const BMP_HEADER_SIZE: 34
+const BUFFER_SIZE: 1920 ; 640 pixels * 3 bytes per pixel
+const FRAMEBUFFER: 0x02000000
+
     opton
+start: mov r19, start
+    pop r20
+    pop r2
+    cmp r2, 0
+    ifz jmp usage_error
+    mov r31, 3
+arg_loop:
+    pop r1
+    cmp r1, 0
+    ifnz jmp usage_error
+    loop arg_loop
 
-    ; open the specified file and draw it
-    ; if the file can't be opened, then just exit
+    ; open the specified file and read the header
     call get_current_disk_id
     mov r1, r0
-    pop r0
-    pop r0
-    mov r2, bg_file_struct
+    mov r0, r2
+    mov r2, bg_file
     call open
     cmp r0, 0
-    ifz call end_current_task
+    ifz jmp file_not_found_error
+    ; read the header of the file to our buffer
+    mov r0, BMP_HEADER_SIZE
+    mov r1, bg_file
+    mov r2, buffer
+    call read
+    mov r30, buffer
+
+    ; parse the header and info header
+    ; magic number "BM"
+    mov r1, parse_error_bad_header_str
+    mov r0, 0x4d42
+    call bmp_assert_16
+    ; file size in bytes (we choose to ignore it instead of verifying it)
+    add r30, 4
+    ; reserved: must be 0
+    mov r0, 0
+    call bmp_assert_32
+    ; bitmap data offset, info header size (ignored for now since we don't support color tables), image width, image height
+    mov r29, [r30]
+    mov r27, [r30 + 8]
+    cmp r27, 640
+    ifgt mov r23, 640
+    iflteq mov r23, r27
+    mov r28, [r30 + 12]
+    add r30, 16
+    ; number of planes
+    mov r1, parse_error_bad_info_header_str
+    mov r0, 1
+    call bmp_assert_16
+    ; bits per pixel (we currently only support 24 and 32 bit RGB)
+    movz.16 r0, [r30]
+    cmp r0, 24
+    ifz mov r24, 3
+    ifz jmp bpp_end
+    cmp r0, 32
+    ifz mov r24, 4
+    ifz jmp bpp_end
+    mov r1, unsupported_bpp_str
+    jmp parse_error
+bpp_end:
+    add r30, 2
+    ; TODO: properly handle compression type
+    mov r1, unsupported_compression_str
+    mov r0, 0
+    ; call bmp_assert_32
+    add r30, 4
 
-    ; read the background file directly into the background framebuffer
-    mov r0, 1228800 ; 640x480x4
-    mov r1, bg_file_struct
-    mov r2, 0x02000000
+    ; draw 24 or 32 bpp image
+    ; calculate line stride
+    mov r26, r27
+    mul r26, r24
+    mov r0, r26
+    and r0, 3
+    cmp r0, 0 ; TODO: align to 4 bytes
+    ifnz jmp parse_error
+    ; find top-most bitmap line
+    mov r0, r26
+    mov r1, r28
+    dec r1
+    mul r0, r1
+    add r29, r0
+    ; cap to framebuffer height
+    cmp r28, 480
+    ifgt mov r28, 480
+    mov r25, FRAMEBUFFER
+    mov r11, 480
+draw_background_line:
+    mov r10, r29
+    mov r12, r28
+draw_bitmap_line:
+    call save_state_and_yield_task
+    mov r0, r10
+    mov r1, bg_file
+    call seek
+    ; find number of pixels to draw
+    mov r0, r23
+    mul r0, r24
+    mov r2, buffer
     call read
+    mov r0, 640
+draw_background_line_loop:
+    mov r30, buffer
+    cmp r0, r23
+    ifgt mov r31, r23
+    iflteq mov r31, r0
+draw_bitmap_line_loop:
+    mov.8 [r25], [r30 + 2]
+    mov.8 [r25 + 1], [r30 + 1]
+    mov.8 [r25 + 2], [r30]
+    add r30, r24
+    add r25, 4
+    loop draw_bitmap_line_loop
+
+    sub r0, r23
+    ifgt jmp draw_background_line_loop
+
+    dec r11
+    ifz call end_current_task
+    dec r12
+    ifnz sub r10, r26
+    ifnz jmp draw_bitmap_line
+    jmp draw_background_line
 
+usage_error:
+    mov r0, usage_str
+    call print 
     call end_current_task
 
-bg_file_struct: data.fill 0, 32
+file_not_found_error:
+    mov r0, file_not_found_error_str
+    call print
+    call end_current_task
+
+parse_error:
+    mov r0, parse_error_str
+    call print
+    mov r0, r1
+    call print
+    call end_current_task
+
+; inputs:
+; r0: expected value (lower 2 bytes)
+; r1: error string
+bmp_assert_16:
+    cmp.16 r0, [r30]
+    ifnz jmp parse_error
+    add r30, 2
+    ret
+    
+; inputs:
+; r0: expected value
+; r1: error string
+bmp_assert_32:
+    cmp r0, [r30]
+    ifnz brk
+    ifnz jmp parse_error
+    add r30, 4
+    ret
+
+; print a null terminated string to the stream
+; inputs:
+; r0: pointer to string
+print:
+    push r0
+    push r1
+    push r0
+    call strlen
+    pop r2
+    mov r1, r20
+    call write
+    pop r1
+    pop r0
+    ret
+
+; find the length of a null terminated string
+; inputs:
+; r0: pointer to string
+; outputs:
+; r0: length of string
+strlen:
+    push r1
+    mov r1, r0
+strlen_loop:
+    cmp.8 [r1], 0
+    ifz jmp strlen_end
+    inc r1
+    jmp strlen_loop
+strlen_end:
+    sub r1, r0
+    mov r0, r1
+    pop r1
+    ret
+
+bg_file: data.fill 42, 32
+buffer: data.fill 65, BUFFER_SIZE
+
+usage_str: data.str "usage: bg <image>" data.8 10 data.8 0
+file_not_found_error_str: data.str "error: file not found" data.8 10 data.8 0
+parse_error_str: data.str "image parse error: " data.8 0
+parse_error_bad_header_str: data.str "bad header" data.8 10 data.8 0
+parse_error_bad_info_header_str: data.str "bad info header" data.8 10 data.8 0
+unsupported_bpp_str: data.str "only support 24bpp and 32bpp" data.8 10 data.8 0
+unsupported_compression_str: data.str "compression not supported" data.8 10 data.8 0
 
     #include "../../../fox32rom/fox32rom.def"
     #include "../../fox32os.def"
diff --git a/base_image/startup.bat.default b/base_image/startup.bat.default
index 9f3f3e0..dc8dfe7 100644
--- a/base_image/startup.bat.default
+++ b/base_image/startup.bat.default
@@ -1,4 +1,4 @@
-*bg bg.raw;
+*bg bg.bmp;
 *barclock;
 *fetcher boot;
 *terminal;